I see various posts regarding NIS 2009 and Firefox problems. For what it is worth this was my experience. Up to recently was an XP SP3 user with NIS2008 and Firefox 3.0.4. Upgraded to NIS2009 with only the usual hassles and Firefox continued to function. Then I upgraded to Firefox 3.0.5 and Firefox hung during startup - really hung - could not be cancelled thru Task Manager. Fiddled around and found only one solution. Changed Norton Firewall settings for Firefox from "Auto" to "Allow". So now I can use Firefox again, which with the current hysteria about IE is a relief. I also tried Firefox 3.1 beta2 but that had same problems as with 3.0.5.