I was having similar problems. I have updated to NIS2009 via a download from Symantec, which is free if you have a current 2008 subscription, i.e it uses the same product key. Browser speeds have improved and Windows start-up is far faster. It also has a crude performance monitor, which shows how much of your processing power is being used by Norton.
I also find CTRL+F5 can sometimes improve the link response, presumably by rerouting the request.
Of course the performance improvements could all be a coincidence!