I was able to log in fine just now.
I would suggest the following:
1. Do the usual cleanup - delete cookies, etc.
2. Try logging in again.
3. If doesn't work, create a dummy account with fictitious data and try logging in (or try a friend/relative's existing account).
4. If the dummy and original account logins fail, you probably have an environmental issue.
5. If the dummy account works and the original account fails, there's probably bad data in your account.
6. Contact Customer Service again.