Have you seen

• Install Firefox on Linux

That explains you may need to track down the c library required.

Another point is; speaking as an Ubuntu 64bit user; I noted that Mozilla automated downloads offered only a 32bit browser, whereas Firefox is also available as a 64bit version that I currently have installed. I had to obtain that from the Mozilla ftp server.

If you had an earlier 64bit version of Firefox installed, that you have now removed is it possible you have now downloaded a 32bit version ?

It is not considered normal, but it is quite possible to run multiple Firefox versions.

Make sure that you have 32 bit versions of the required libraries.

Check the system requirements.

• http://www.mozilla.org/en-US/firefox/19.0.2/system-requirements/

I figured it out. I forgot I installed the older versions as root user. I was trying to install new version as regular user. the key was the Permission error. regular user didn't have permissions to the required libraries.