Network OK, but Internet Not

I have network connection I can ping addresses on the network as well as like yahoo.com but everytime I go to use IE or firefox I get a DNS error. The laptop used to have norton internet security but it was killing the speed so I disabled it. the net worked great for about 24hours then starting doing the above. I can't actually uninstall NAV as it states there is a problem with the installer or the windows installer. any suggestions? oh net works fine in safe mode with networking but not in any full blow run. did a hijack this nothing out of the usual. tried replacing the 'host' file no joy there either AVG turned up no baddies Spybot is working on it now. any help would be appreciated

Jam it back in, in the dark.

Thanks for the help. It was norton still hanging on in the backgroud, re-enabled it and disabled all the features this was a painfully slow task but once done fixed the problem. Then downloaded the uninstall program from symatec and removed it. Laptop works much better now thanks all.

How ya doing, buddy?