I hate Norton, your choice, your problem.
I use McAfee, my choice I never have a problem with viruses.
Tried Yahoo AntiSpy yet?
When was the last time you did a disk cleanup?
And a Defragment?
Either way you need you need to scan your PC for spyware and trojans, do a complete disk cleanup and defrag and then run a virus scan.
Start, all programs, accessories, system tools, disk cleanup and defrag are both located in this folder.
Clean out your browser cache, go up to SAFETY at the top of the page and find DELETE BROWSING HISTORY delete everything on that list as often as possible you may deside not to do Passwords but is you want to make sure someone is not running a hijack on you do so at the risk you choose.
Yahoo AntiSpy toolbar is free and guaranteed free for LIFE!! It cleans up trojans and spyware, malware, worms and adware and should be run 4 times a day if you surf lots.
If you have an internet connectivity issue it may also need to be looked at by your IP company if they haven't done so already.
Most internet providers will wine and complain and say they don't know or can't fix an issue but if you have a crap connection it is their fault, get a Cable Modem connection no DSL or dialup and get away from paying for satellite Internet too cuz when it rains or is cloudy you can't get a signal either.
Basically if you use a local company you are not using a cable connection the cable connection is 5 times faster and runs lots better!!
If you have a corrupt file it can also cause issues.
type in the run box chkdsk /f /r exactly as you see it here, you may have to restart and it will do the whole deal by itself and find and fix all corrupted files.
P.S. Beware anyone stating they want you to download any programs that you are not familiar with their main company. Yahoo is a trusted and certified company and has the highest trust rating online. You choose!
Good luck hope you resolve your issues.