Comment 33 for bug 109943

As of yesterday, I've gotten fed up with the resource hogishness and stability issues of the default Ubuntu window and desktop managers. I've now installed and configured OpenBox.

Where I was seeing this issue 3 days ago (albeit not as pronounced as once-upon-a-time), I'm now do not notice anything. Other than a 4 or 5 second wait to quit TB, things are right-zippy, with no (known) loss of functionality. I don't know how to confirm, but this certainly leads me to suspect an interaction between Thunderbird and Gnome and Unity. (And I believe KDE too, but it's now 4 years since I last tried KDE ...)

Another data point.