Event message: An unhandled access exception has occurred (IIS 7.5, cannot load website)

The local users group needed modify permissions to get past this error. Resolved.

I would just like to clarify for anyone else who comes to this question. The permissions need to be changed on the folder where the website resides in windows explorer.

I had this exact error - the only solution that worked was setting the app pool's Enable 32-bit Applications advanced setting to True.

Update: As I continue to have issues with a particular solution, I've found that clearing the C:\WINDOWS\Microsoft.NET\Framework\v4.xxx.xx\Temporary ASP.NET Files\ resolves the issue in most cases.