Firefox pages not loading

Suddenly, about two weeks ago Firefox 10 stopped loading web pages. The "connecting" circle keeps spinning and absolutely nothing happens. I love Firefox and have to say that this is one of the most bizarre computing frustrations I've ever experienced. I have Thunderbird email and may have found a temporary way around it: I right click on "Reload tab" on the website tab I'm trying to access. I have to do it several times for it to connect to the site. I uninstalled FF 10 and reinstalled 9 to see if the problem persisted: it does.
I actually had to use Internet Explorer (!) a few times to be able to access the various websites, and I downloaded Chrome as a temporary stop-gap measure in case FF doesn't work at all. Although I don't want to use any browser but Firefox, this malfunctioning is getting me down a lot; I might be going to Chrome permanently. What can be causing this vexing problem of web pages not loading? [I have Windows 7 Profession 32 bit SP1] Thanks for your ideas. ec

First thing to check is your firewall:

Firewalls - MozillaZine Knowledge Base

Next step:

Standard diagnostic - Firefox - MozillaZine Knowledge Base

Firewalls, Make sure you clear everything. That may help.

Try reading Post #7 from this thread may help.