Same for me, happens sporadically, no rhyme or reason. I don't think it's specific to Ubuntu however, and is a bug in Thunderbird itself. Have had the same thing happen to me periodically on Linux distros I built based on Puppy Linux. My add-ons are:
Lightning Lookout Provider for Google Calendars (disabled) SMTP select SyncKolab Timezone definitions for Mozilla Calendar Toolbar Buttons -- new messages not able to type https://bugs.launchpad.net/bugs/271034 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
