IE opens up and works fine, and I checked to ensure the firewall wasn't blocking firefox's access.
I went into Application Data>Mozilla Firefox, saved the profile info on a flash drive, then deleted the info from the computer (in case one of the themes or something had been corrupted) and tried to open the browser, still didn't work.
I tried to open in Safe Mode, I saw the hourglass, then received the message that firefox was already open (it wasn't, I checked the task manager, the background running processes, it wasn't down as running) so I restarted the computer.
Then I uninstalled and reinstalled firefox 3.0.6; this time it asked me whether to put it as default browser and/or import settings from IE; when I answered no I saw the hourglass, and then nothing else happened.
I've been trying off and on all day, and it's still happening.