For me (so far), it seems that this has been fixed with Thunderbird 11.0.1 and Ubuntu 12.04.
thunderbird 11.0.1+build1-0ubuntu2 unity 5.10.0-0ubuntu6
For me (so far), it seems that this has been fixed with Thunderbird 11.0.1 and Ubuntu 12.04.
thunderbird 11.0.1+ build1- 0ubuntu2
unity 5.10.0-0ubuntu6