TDC logs me out after I haven't done much in a while, I download and play a game and when I try to comment it goes "This is a members only area" and then I have to log back in. I think this should be fixed... if no one noticed already.
Make sure your browser is set to both allow cookies and keep them for a long period of time. If you have extremely low room reserved for them, or aren't saving them in the first place, it will log you out.
I never changed the browsers settings, Though I have looked at them. It says "Keep cookies until they expire" and I am viewing TDC from create-games.com; The clock on my comp is also set correctly. Though I haven't been logged out any other time than when I download a game and play it for a while.