I recomend downloading and installing the latest version of firefox, if you still have problems, email your problem to them.
Beinging open-source, and having a policy to be the most stable browser around, they'll be more than happy to personly solve your problem.
What I've noticed using firefox, that it is non-responsive for a short time loading slow web-pages, maybe if your wait a little longer it'll become responsive agian showing the web-page/timeout message.
Hope that will help - phizz
p.s. A Dell is just like any other computer with its hardware. The preinstalled software and possible hidden changes they've done with windows might be the problem (this is a guess), who knows what dell does with the windows package they install on people computer. If you format and install windows (not using the recovery discs) you'll have a much more cleaner computer without the useless extra junk dell shoves on there.