Comment 2 for bug 609941

I experienced the same issue and did:

$ sudo aptitude remove firefox

$ sudo aptitude install firefox

Upon the install command I was presented with:

The following actions will resolve these dependencies:

Upgrade the following packages:
firefox-3.0 [3.5.9+nobinonly-0ubuntu0.9.10.1 (now) -> 3.6.7+build2+nobinonly-0ubuntu0.9.10.1 (karmic-security,
karmic-updates)]
firefox-3.5 [3.5.9+nobinonly-0ubuntu0.9.10.1 (now) -> 3.6.7+build2+nobinonly-0ubuntu0.9.10.1 (karmic-security,
karmic-updates)]
firefox-3.5-branding [3.5.9+nobinonly-0ubuntu0.9.10.1 (now) -> 3.6.7+build2+nobinonly-0ubuntu0.9.10.1
(karmic-security, karmic-updates)]
firefox-3.5-gnome-support [3.5.9+nobinonly-0ubuntu0.9.10.1 (now) -> 3.6.7+build2+nobinonly-0ubuntu0.9.10.1
(karmic-security, karmic-updates)]

Score is 150

Accept this solution? [Y/n/q/?]

and I accepted the proposed solution.