Probably some weird preference problem. While on vacation my wife and I share a MacBook Pro running 10.4.11 with 2 separate accounts. She does not have a problem with Thunderbird mail. Recently, every time I click on Send, I time out without the mail going through. The only way around it that I know, and it works every time, is to go to MenuBar>Tools>Account Settings and when it opens, just click on ok and then I can send that e-mail. I trashed Thunderbird 2.x and installed 3.0.4 but the problem remains. I've also rewritten the SMTP server setting.