did you follow the full directions in the link to symantec you supplied, often times you have to manually do stuff, even if they say you don't, like all the registry stuff, i would go in and do that first, then run norton, and DON'T quarantine, delete them if possible, if it won't let you delete, then quarantine the files, but right after that, get rid of all the quarantined files
also you could try another antivirus software program, i use it all the time and i think it is better than norton, it is called AVG, by www.grisoft.com and it's free