BleepingComputer.com: Firefox is unable to connect.

So, a while ago, my computer was being all weird, and wouldn't let me install things in normal mode.
Well, it seems I can now, so I tried installing firefox again (I've been stuck with internet explorer for a while).
However, after opening Firefox, no matter what site I try to go to, it tells me this....

"Unable to connect

Firefox can't establish a connection to the server at www.google.com.

* The site could be temporarily unavailable or too busy. Try again in a few
moments.

* If you are unable to load any pages, check your computer's network
connection.

* If your computer or network is protected by a firewall or proxy, make sure
that Firefox is permitted to access the Web."

Internet explorer works just fine though. I can always connect, no problem.
I have the default firewall for windows XP, although I can't remember how to check if it accepts firefox.
I don't believe it's my virus protection, because none of it is the active kinda besides avira. (malwarebytes, spyeware doctor, Avira).

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plus Firefox issue = I suggest, you start new topic in "Am I Infected?" forum.