Firefox won't connect to certain sites

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[bball2]

Try using another browser to see if it's actually the browser (ie. Opera or Safari), if it is actually Firefox that's the problem, clear cache, try again, if it doesn't work, clear cookies, and try again.

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[GoChris]

even the free anti virus programs out there are better than norton. if you have a router, you don't need their internet security at all. I'd recommend not using norton.
try AVG

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[bball2]

Just got a new computer, one of the first things I did was remove every single last trace of Norton from the hard disc

[bigbadboss101]

I had the same problem last week but I was using IE. It turns out to be my firewall/spyware blocker. In this case it might be your Norton. I had since removed the apps and replace with something else.