Firefox crashes each/every time I try to use it.

When clicking on any link in an e-mail this is what I get (plus the choice of quitting or restarting Firefox and the option to "send a report," as indicated):
"We're Sorry

"Firefox had a problem and crashed. We'll try to restore your tabs and windows when it restarts.

"To help us diagnose and fix the problem, you can send us a crash report."

I've tried to switch to Internet Explorer (which I can use more or less successfully) but Firefox remains prominent for links in e-mail messages.

I've used Firefox 3.0.5 (I think but it could have been 3.0.9) and also a Beta version -- neither work now and I can't seem to find out which version is left on the machine. I am using Windows XP.

Also, when I place the cursor over some links, it produces (briefly) a lengthy "note" that says it is blocked ... something like this: "blocked::http://e2ma.net/go/1917903544/ etc." (it goes away too fast to collect it all). And, of course, if I click on it, I get the "crashed" message above.

HELP!