CheckGmail is a nice little utility for... well, I'm sure you can guess what for. The version in the Debian Squeeze repository wouldn't let me log in and kept telling me the username or password was wrong.
The update command that's supposed to cure the problem according to the website didn't work on my system, I think because I don't have Sudo set up.
There's a method of manually updating the program described on this site.
That didn't work until I'd applied a patch as described here.