Since I installed Mozilla Firefox 3.5, I've been having constant Server Not Found problems. Judging by internet forums, it's a very common problem.
Lily Poberezhska
Mozilla has some support documents at "Server not found", with suggested approaches. There's also "Cannot connect after upgrading Firefox", which deals with firewall problems. However, I've found that there are fewer problems with more recent versions, and the latest 3.5.5 also seems faster. If you don't have a router problem (which can lead to Internet Explorer not working as well) then the best solution is probably to uninstall Firefox, delete all the add-ons, then reinstall the latest version.
