I can confirm David Wallace's assertion that this seems to happen after the computer wakes from idle.
The first email I try to send at that point freezes my machine for approximately 1.5 minutes. Then the email goes through and my system is back. It seems that it is actually going through the window animation in extreme slow motion... -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/963736 Title: thunderbird freezes at random : must be killed and reload To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/firefox/+bug/963736/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs