I’m going to get a little nerdy here.  If you aren’t interested in doing a restore to a SQL database then you should skip this post!

I have this problem everytime I do a restore of a SQL database.  The short version is that the logins get screwed up.  I can’t use the user level security I’ve setup.

I found this link: http://support.microsoft.com/kb/274188 which says:
“Troubleshooting Orphaned Users” Topic in Books Online is Incomplete

GREAT!!!!  Why not just make it complete???

So anyway, fixing the Orphaned Users will resolve this problem.

Good luck!