I have a Gmail account with dots in the name, a la joe.blow@gmail.com. I don't know that the dots are the reason T-Bird can't connect to this account, but I've successfully connected to a personal Gmail account that doesn't have dots in the name as well as a business account and a Yahoo account.

So T-Bird's working. It can find the recommended IMAP/POP configurations for Gmail, no prob, but when I click "Done," invariably I get an error that the username or password is invalid. Both are fine and work when logging in to Gmail and setting up an IMAP account in Outlook. The only difference I can see between this and my other Gmail account is the dots. But if the dots are fine, what else should I check? Thanks!