Originally Posted by
Maelstrom
What security level do you have in your browser? Do you accept cookies?
This reads more like a client side issue than a server issue. Its your browser that stores and maintains cookies, not the server.
I'll second this. Most likely your computer clearing the log-in cookie often. That or if you've changed your password recently, there may be an old cookie hiding somewhere that's trying to log you in under your old password that's getting bounced. Try clearing ALL temporary internet files and checking the security settings.