Is you assembly in the GAC or did you bin deploy it?  

If it's a bin deploy, did you sign the assembly and configure the code access security?

Problem with XslTransform
I've tried to install Pantheon desktop environment several times. I tried sudo apt-get update and sudo apt-get upgrade, but it's no use. I’m just a very new beginner. This is what I’ve done:

quanglong@ubuntu:~$ sudo add-apt-repository ppa:elementary-os/daily
[sudo] password for quanglong: 
You are about to add the following PPA to your system:
 ATTENTION!
Do NOT install this PPA if you want a tested running system, this PPA contains the newest and most unstable development of elementary, it's useful only if you are a developer and are not afraid to encounter CRITICAL BUGS.
Also this PPA may overwrite already installed packages you don't want it to!
 More info: https://launchpad.net/~elementary-os/+archive/daily
Press [ENTER] to continue or ctrl-c to cancel adding it

gpg: keyring `/tmp/tmpkz5d_z/secring.gpg' created
gpg: keyring `/tmp/tmpkz5d_z/pubring.gpg' created
gpg: requesting key 4E1F8A59 from hkp server keyserver.ubuntu.com
gpg: /tmp/tmpkz5d_z/trustdb.gpg: trustdb created
gpg: key 4E1F8A59: public key "Launchpad PPA for elementary OS team" imported
gpg: Total number processed: 1
gpg:               imported: 1  (RSA: 1)
OK
/bin/rm: cannot remove `/run/user/root/gvfs': Is a directory
quanglong@ubuntu:~$ sudo apt-get update
Hit http://ppa.launchpad.net quantal Release.gpg                               
Get:1 http://security.ubuntu.com quantal-security Release.gpg [933 B]          
Hit http://us.archive.ubuntu.com quantal Release.gpg                           
Hit http://ppa.launchpad.net quantal Release.gpg
Get:2 http://security.ubuntu.com quantal-security Release [49.6 kB]
Get:3 http://us.archive.ubuntu.com quantal-updates Release.gpg [933 B]       
Hit http://us.archive.ubuntu.com quantal-backports Release.gpg                 
Hit http://ppa.launchpad.net quantal Release             
Hit http://us.archive.ubuntu.com quantal Release                               
Hit http://ppa.launchpad.net quantal Release                                   
Get:4 http://us.archive.ubuntu.com quantal-updates Release [49.6 kB]           
Hit http://ppa.launchpad.net quantal/main Sources                             
Get:5 http://security.ubuntu.com quantal-security/main Sources [74.3 kB]      
Hit http://ppa.launchpad.net quantal/main amd64 Packages                       
Hit http://ppa.launchpad.net quantal/main i386 Packages                        
Hit http://us.archive.ubuntu.com quantal-backports Release                     
Hit http://us.archive.ubuntu.com quantal/main Sources                          
Hit http://us.archive.ubuntu.com quantal/restricted Sources                    
Hit http://us.archive.ubuntu.com quantal/universe Sources
Hit http://ppa.launchpad.net quantal/main Sources                              
Hit http://us.archive.ubuntu.com quantal/multiverse Sources           
Get:6 http://security.ubuntu.com quantal-security/restricted Sources [1,833 B]
Hit http://us.archive.ubuntu.com quantal/main amd64 Packages                   
Hit http://ppa.launchpad.net quantal/main amd64 Packages              
Hit http://us.archive.ubuntu.com quantal/restricted amd64 Packages
Get:7 http://security.ubuntu.com quantal-security/universe Sources [23.8 kB]
Hit http://ppa.launchpad.net quantal/main i386 Packages                       
Hit http://us.archive.ubuntu.com quantal/universe amd64 Packages              
Hit http://us.archive.ubuntu.com quantal/multiverse amd64 Packages             
Get:8 http://security.ubuntu.com quantal-security/multiverse Sources [1,169 B]
Hit http://us.archive.ubuntu.com quantal/main i386 Packages                    
Hit http://us.archive.ubuntu.com quantal/restricted i386 Packages     
Get:9 http://security.ubuntu.com quantal-security/main amd64 Packages [207 kB]
Hit http://us.archive.ubuntu.com quantal/universe i386 Packages               
Hit http://us.archive.ubuntu.com quantal/multiverse i386 Packages              
Hit http://us.archive.ubuntu.com quantal/main Translation-en                   
Hit http://us.archive.ubuntu.com quantal/multiverse Translation-en             
Hit http://us.archive.ubuntu.com quantal/restricted Translation-en             
Hit http://us.archive.ubuntu.com quantal/universe Translation-en               
Get:10 http://us.archive.ubuntu.com quantal-updates/main Sources [134 kB]      
Get:11 http://security.ubuntu.com quantal-security/restricted amd64 Packages [3,469 B]
Get:12 http://security.ubuntu.com quantal-security/universe amd64 Packages [72.4 kB]
Ign http://ppa.launchpad.net quantal/main Translation-en_US                    
Get:13 http://us.archive.ubuntu.com quantal-updates/restricted Sources [2,564 B]
Ign http://ppa.launchpad.net quantal/main Translation-en                       
Get:14 http://us.archive.ubuntu.com quantal-updates/universe Sources [96.7 kB] 
Ign http://ppa.launchpad.net quantal/main Translation-en_US                    
Get:15 http://security.ubuntu.com quantal-security/multiverse amd64 Packages [1,488 B]
Ign http://ppa.launchpad.net quantal/main Translation-en                       
Get:16 http://security.ubuntu.com quantal-security/main i386 Packages [205 kB] 
Get:17 http://us.archive.ubuntu.com quantal-updates/multiverse Sources [5,269 B]
Get:18 http://us.archive.ubuntu.com quantal-updates/main amd64 Packages [337 kB]
Get:19 http://us.archive.ubuntu.com quantal-updates/restricted amd64 Packages [4,804 B]
Get:20 http://us.archive.ubuntu.com quantal-updates/universe amd64 Packages [218 kB]
Get:21 http://security.ubuntu.com quantal-security/restricted i386 Packages [3,531 B]
Get:22 http://security.ubuntu.com quantal-security/universe i386 Packages [73.0 kB]
Get:23 http://us.archive.ubuntu.com quantal-updates/multiverse amd64 Packages [12.1 kB]
Get:24 http://security.ubuntu.com quantal-security/multiverse i386 Packages [1,726 B]
Hit http://security.ubuntu.com quantal-security/main Translation-en            
Get:25 http://us.archive.ubuntu.com quantal-updates/main i386 Packages [334 kB]
Hit http://security.ubuntu.com quantal-security/multiverse Translation-en      
Hit http://security.ubuntu.com quantal-security/restricted Translation-en      
Hit http://security.ubuntu.com quantal-security/universe Translation-en        
Get:26 http://us.archive.ubuntu.com quantal-updates/restricted i386 Packages [4,841 B]
Get:27 http://us.archive.ubuntu.com quantal-updates/universe i386 Packages [219 kB]
Get:28 http://us.archive.ubuntu.com quantal-updates/multiverse i386 Packages [12.3 kB]
Hit http://us.archive.ubuntu.com quantal-updates/main Translation-en           
Hit http://us.archive.ubuntu.com quantal-updates/multiverse Translation-en     
Hit http://us.archive.ubuntu.com quantal-updates/restricted Translation-en     
Hit http://us.archive.ubuntu.com quantal-updates/universe Translation-en       
Hit http://us.archive.ubuntu.com quantal-backports/main Sources                
Hit http://us.archive.ubuntu.com quantal-backports/restricted Sources          
Ign http://security.ubuntu.com quantal-security/main Translation-en_US         
Hit http://us.archive.ubuntu.com quantal-backports/universe Sources            
Ign http://security.ubuntu.com quantal-security/multiverse Translation-en_US   
Hit http://us.archive.ubuntu.com quantal-backports/multiverse Sources          
Ign http://security.ubuntu.com quantal-security/restricted Translation-en_US   
Hit http://us.archive.ubuntu.com quantal-backports/main amd64 Packages         
Ign http://security.ubuntu.com quantal-security/universe Translation-en_US     
Hit http://us.archive.ubuntu.com quantal-backports/restricted amd64 Packages   
Hit http://us.archive.ubuntu.com quantal-backports/universe amd64 Packages     
Hit http://us.archive.ubuntu.com quantal-backports/multiverse amd64 Packages   
Hit http://us.archive.ubuntu.com quantal-backports/main i386 Packages          
Hit http://us.archive.ubuntu.com quantal-backports/restricted i386 Packages    
Hit http://us.archive.ubuntu.com quantal-backports/universe i386 Packages      
Hit http://us.archive.ubuntu.com quantal-backports/multiverse i386 Packages    
Hit http://us.archive.ubuntu.com quantal-backports/main Translation-en         
Hit http://us.archive.ubuntu.com quantal-backports/multiverse Translation-en   
Hit http://us.archive.ubuntu.com quantal-backports/restricted Translation-en   
Hit http://us.archive.ubuntu.com quantal-backports/universe Translation-en     
Ign http://us.archive.ubuntu.com quantal/main Translation-en_US                
Ign http://us.archive.ubuntu.com quantal/multiverse Translation-en_US
Ign http://us.archive.ubuntu.com quantal/restricted Translation-en_US
Ign http://us.archive.ubuntu.com quantal/universe Translation-en_US
Ign http://us.archive.ubuntu.com quantal-updates/main Translation-en_US
Ign http://us.archive.ubuntu.com quantal-updates/multiverse Translation-en_US
Ign http://us.archive.ubuntu.com quantal-updates/restricted Translation-en_US
Ign http://us.archive.ubuntu.com quantal-updates/universe Translation-en_US
Ign http://us.archive.ubuntu.com quantal-backports/main Translation-en_US
Ign http://us.archive.ubuntu.com quantal-backports/multiverse Translation-en_US
Ign http://us.archive.ubuntu.com quantal-backports/restricted Translation-en_US
Ign http://us.archive.ubuntu.com quantal-backports/universe Translation-en_US
Fetched 2,151 kB in 45s (47.7 kB/s)
Reading package lists... Done
/bin/rm: cannot remove `/run/user/root/gvfs': Is a directory
quanglong@ubuntu:~$ sudo apt-get install elementary-desktop
Reading package lists... Done
Building dependency tree       
Reading state information... Done
E: Unable to locate package elementary-desktop
/bin/rm: cannot remove `/run/user/root/gvfs': Is a directory
quanglong@ubuntu:~$ 

