Could not load file or assembly Temporary ASP.NET Files
I had simmilar problem after i tried to start performance tests.I removed assemblyPostProcessorType attribute in system.web > compilation element in web.config and it worked again.
<system.web><compilation debug="false" targetFramework="4.5.1" assemblyPostProcessorType="Microsoft.VisualStudio.Enterprise.Common.AspPerformanceInstrumenter, Microsoft.VisualStudio.Enterprise.AspNetHelper, Version=12.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" /></system.web>
If you use Visual Studio Performance Tools then it is possible that Visual Studio left a key in your web.config appsettings section. It causes a 32 bit library to load, which won't work if your application is loading in 64 bit mode.
Check for the following and remove it:
<add key="Microsoft.VisualStudio.Enterprise.AspNetHelper.VsInstrLocation" value="C:\Program Files (x86)\Microsoft Visual Studio 11.0\Team Tools\Performance Tools\vsinstr.exe"/>
One of the solution is to delete those files from temporary asp.net folder that always works for me.