You're probably talking about this bug : https://bugs.launchpad.net/ubuntu/+source/firefox/+bug/129007 And you're apparently right ! Switching theme to Clearlooks solved the issue.
I thought it was not related to themes because I tried 4 of them, but all triggered the bug... sorry for the duplicate, and thanks for solving my problem so quickly :)
You're probably talking about this bug : https:/ /bugs.launchpad .net/ubuntu/ +source/ firefox/ +bug/129007
And you're apparently right ! Switching theme to Clearlooks solved the issue.
I thought it was not related to themes because I tried 4 of them, but all triggered the bug... sorry for the duplicate, and thanks for solving my problem so quickly :)