Comment 4 for bug 931637

I don't think this is only triggered by firebug. Clicking on Firebug's DOM tab is a sure crasher.

Even with firebug disabled, for e.g. other addons such as Awesome Screeshot from Diigo. Take a screenshot -> click Done -> Close Tab and the browser crashes.

Everytime I am closing the browser, it crashes and notifies to submit a bug report:

Here are some that have been uploaded already -

http://crash-stats.mozilla.com/report/index/bp-6ff8f906-cb26-4864-82ed-31db72120213
http://crash-stats.mozilla.com/report/index/bp-5a9ac084-5c83-42e9-9295-923132120213

Am moving to official build till we see some solution to this as FF is unsuable on Ubuntu as of now.