Hit this. You can find the location in localstore.rdf where sizemode="fullscreen", and set it back to "normal", instead of just blowing away the thing.
** Changed in: thunderbird (Ubuntu) Status: Incomplete => Confirmed -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/196058 Title: Thunderbird starts in a full-screen mode and cannot be restored -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs