Hello. I'm running a dual-boot with Windows 7 and Linux Mint Debian.
My firefox version is 3.6.8
If from my firefox browser I go to Help/CheckforUpdates, I get the following message:

"Unable to Update"
A recommended security and stability update is available, but you do not have the system permissions required to install it. . .

does anyone know of a how-to as to how to manually upgrade my firefox to the latest version (including how to purge the existing version from my system)? Thanks for the help.

You update all software through the distribution's package manager, not the update function in individual applications.

Thanks for the help guys. I just went to my terminal, logged in as superuser, and ran firefox. (which was in the /opt/firefox directory)
Then when I went to Help/Check for Updates, it found the update and downloaded it. From there, I exited out of my browser and restarted it. At first I was upset because the version of firefox hadn't changed! Then I noticed that when I went to Help Menu, "Check for Updates" had changed to "Install Downloaded Updates". I clicked on this and the updates were installed. I then chose to restart firefox and, when I checked the version, it was the latest and greatest. The key to the whole thing is to be in superuser mode before invoking firefox.

That isn't the proper way to upgrade packages, and will cause problems down the line. Is there a particular reason you are avoiding doing it the right way?

Perhaps you can give us a quick run down on the proper way, MS3FGX.

Mine always just popped up a window saying updates were available and I clicked to install them.