I'm using Linux Mint 17 (Qiana) in my Oracle Virtual Box. Whenever I try to open an application with sudo, it is not working. For eg. if I try to open sublime text editor using the command sudo subl filename, it is asking for the password. After entering the password, nothing is happening. But if I use subl filename, it is working and it prompts for password when you attempt to save it.When I tried to open Software Manager, it prompted password like this:Nothing happened when I entered the password. So I tried mintinstall from terminal, which again prompted for password like this:After entering the password there, it outputs the following into terminal.Traceback (most recent call last):  File /usr/lib/linuxmint/mintInstall/mintinstall.py, line 32, in <module>    from widgets.pathbar2 import NavigationBar  File /usr/lib/linuxmint/mintInstall/widgets/pathbar2.py, line 1021, in <module>    class PathBarThemeHuman:  File /usr/lib/linuxmint/mintInstall/widgets/pathbar2.py, line 1034, in PathBarThemeHuman    animate = gtk.settings_get_default().get_property(gtk-enable-animations)AttributeError: 'NoneType' object has no attribute 'get_property'So, I'm greatly confused by these things. Please help.
Applications not starting with sudo
linux mint;sudo