Re: Application not working
Check frmMain.cs:line 490 ;)
Did you delete ApplicationName.exe.config?
Re: Application not working
It looks like an assembly is missing, or the framework is corrupted, or some security policy prevents the application from running... There are tons of possible reasons.
You should provide more details, at least what file is missing.\
You could try to use fuslogvw.exe to check the log of assembly resolution failures. (It is part of SDK and should reside somewhere in VisualStudio installation directory).
Also check the konstructor of frmMain, if any file operation is performed here.