Firefox crashes when opening a new tab

[C. Augusto Valdés]

I installed the Ad-aware extension in Firefox (after editing manually in
about:config the value general.useragent.vendorSub to the following value: 1.0.4
in order to be able to access addons.mozilla as referenced in another bug) I
installed the extension and after restarting firefox it was not enabled. even
after a system reboot it wasn't enabled so I ran sudo dpkg-reconfigure
mozilla-firefox in the console. the extension was enabled but now it crashes
whenever I try to open a new tab. as a side note, applications open at the time
of the crash shut down as well.

[Corey Burger (corey.burger)]

This bug has been marked as a duplicate of bug 36208.

[Matthew East (mdke)]

This is not a documentation bug so I'm reassigning it to the correct component.