Firefox isn't working after install with Ubuntuzilla and then complete removal of both along with cleaning profile, executables etc. How to install fresh from Ubuntu repository

To use Thunderbird's latest version I installed Ubuntuzilla. But later I decided to with Ubuntu releases of Firefox and Thunderbird as the name, icons were changed to something I didn't like. I removed Thunderbird. But in case of Firefox, it was in /opt after Ubuntuzilla install with disabled "check updates". It was showing 3.5.6 where 3.5.7 is released. So removed Ubuntuzilla but update still didn't work. I checked source list and removed repos for Ubuntuzilla and Mozilla-Daily ppa (repo) so that only Ubuntu updates will show in Synaptic. Which is mentioned as: (I think this is 3.5.7):

"firefox-3.5 3.5.7+nobinonly-0ubuntu0.9.10.1 safe and easy bro.."

Update still didn't work (not even with system update).
Then tried a fresh Firefox install from repo and so removed /opt/firefox and also in other places. Even, "firefox" and "firefox-3.5" executables from /usr/bin/ and some files from other places. Cleaned my Firefox profile in ~/.mozilla, I have backed up my profile and settings. Installed firefox from the repo and it's not working. May be because links were symlinked to the one in /opt/firefox/ and moreover I have removed "executables", I am not sure.

How can I go back to original Firefox that came with my Ubuntu Live-CD? Cleaning the mess my stupid attempt might have created. Of course with the latest version available and also the updates should work with Ubuntu updates.