Q:

Why did my Visual Studio start acting this way? iisexpress cannot find or open the PDB file

When I first created my project and ran it, I didn't get these messages:

'iisexpress.exe' (CLR v4.0.30319: DefaultDomain): Loaded 'C:\Windows\Microsoft.Net\assembly\GAC_32\System.Web\v4.0_4.0.0.0__b03f5f7f11d50a3a\System.Web.dll'. Cannot find or open the PDB file.

So what did I do to my VS config, or maybe my project properties that caused this issue?
Before this started happening, running the application took a minute or two, now I'm waiting more like 5 mins. Which is nuts, there is something wrong with my config somewhere.

A:

The most likely reason you started getting the message 
"'iisexpress.exe' (CLR v4.0.30319: DefaultDomain): Loaded 'C:\Windows\Microsoft.Net\assembly\GAC_32\System.Web\v4.0_4.0.0.0__b03f5f7f11d50a3a\System.Web.dll'. Cannot find or open the PDB file."  is because that DLL is now being loaded during execution, and wasn't being loaded previously.
The missing PDB file however is not part of your problem.  You can get rid of the warning message by obtaining this PDB file from Microsoft.  But I suggest you focus on what you did to make it start appearing (ie when you started loading System.Web.dll).  This might help explain why it takes longer to load.

