Hi Beth,
The only time you should see activity from the .NET compiler (csc.exe) is when you first deploy a new build or updated files it will compile things into the Temporary ASP.NET files folder down under Windows\Microsoft.NET\Framework[64]\[version]\ and processor usage may be high while it does that but it should not last a long time.
Once everything has been compiled you should not see much activity from the compiler in the task manager. The web site itself is going to be an instance of w3wp.exe in task manager.
Sometimes things can get funky in those temp files and you may see errors about those temp files. Rather than rolling back patches I would try restarting IIS, and if that doesn't solve it I'd try rebooting first and if the problem continues after a reboot, I'd try stopping the web site(s) briefly in IIS and manually deleting the temporary files (you can't delete them while they are in use), and then when you start the sites up it recompiles them again it usually clears things up.
Hope that helps,
Joe