MSN Messenger upgrade won't connect

I've been using MSN Messenger for Mac ever since I got my iMac, and it's been fine. MSN recently had an upgrade, so I downloaded and installed it. I have not been able to connect to MSN ever since.

The error message I get says that either my sign in name or password is incorrect, but that's bunk. I've re-installed it several times, all to no avail.

Has anyone else out there had this problem, and if so, is there a solution?

Thanks.