That assembly does not allow partially trusted callers

I got this error "That assembly does not allow partially trusted callers" when I was trying to install a Windows Service written in C#.  After searching the Internet for a while and trying different solutions such as [assembly: System.security.AllowPartiallyTrustedCallers()] and others, nothing seemed to help.  My problem turned out to be that I was trying to install the service from a mapped network drive. After I copied the service over to the local drive, I was able to install it successfully.