imho:
Forget about norton. It is more trouble then it is worth.
Do you feel safe having a program on your computer that you can NEVER completely uninstall or remove?
It's a pain in the ass and it causes problems with all kinds of programs.
I think you should uninstall it as much as you can. Turn it off and remove it from the boot startup list.
Then check out these two programs:
http://www.avast.com/
http://lavasoft.com/products/ad_aware_free.php
It's all i ever needed.
Both are free and work VERY well. They also don't interfere with other programs or with themselves.
Furthermore you are using
Firefox i hope?