There are some detailed articles for troubleshooting Firefox "hanging" and becoming unresponsive. Here is one with several suggested steps, but first, make a backup of your computer for safekeeping.

To back up Firefox, see Backing up your information.

Troubleshooting: Firefox hangs | Troubleshooting | Firefox Help

I also would note that you're using a pretty old version of Firefox. If you're not ready for Firefox 4, have you tried 3.6? You can grab it here:

http://www.mozilla.com/firefox/all-older

I have had better luck out of the earlier 3.2/3.4 ??? version. I have uninstalled, reinstalled, updated, plug-in checked/updated and still the same results. Tried chrome, and having the same issues with it as well. Explorer crashes my system and loses lots of momentum when it will run. I have always chosen firefox as my primary browser. I will read these articles and try a few things, but if you can think, or any one can give any suggestions, I'm all ears...All suggestions Welcomed!! Thanks