I am using Mozilla Firefox 3.6 version I don't know why it hangs and crash after downloading some pages. Mozilla Firefox Is not able to load pages which contain lot of advestisements or various other script.My Mozilla Firefox Hangs about 2-3 times when I surf on web during one hours.You can removed Mozilla Firefox Hanging & Crashing problem.Here is a firefox website link which will help you to solve your hanging problem
First check out your problem and then try fixing solution.
You can try there also
Clear your private data like cache and history.
Remove all add-ons,plugins that are not compatible with this version of Mozilla firefox.
Reinstall Mozilla firefox.
If you have any other solution to this Mozilla Firefox Hanging & Crashing problem.
Feel free to share.