Well a couple of notes to make here then. I would try removing norton completely. In the add/remove programs clicky under the control panel there will be a couple of things. One will probably say Norton Anti-virus blah blah and the other symatech liveupdate version yada yada. You want to remove everything related to norton at this point.
Then I would ditch the yahoo messanger too at this point. Completly uninstall it the same way as with norton.
I would even go so far as to go into the program files folder and remove the empty (or partially empty..dont worry..it happens) norton and YIM file folders...then empty the recycle bin again.
From that point, reboot and see if everything is working good. Make sure no more problems and then at least you will be able to eliminate programs as problems if you get the error message after reinstalling norton/yim, etc.
Also, I would lose the norton 2002. I have 2003 and it has virus protection not only for the puter but for IM programs as well. As far as the YIM goes, I dont use it...I use Trillian. You might want to check it out at
http://www.ceruleanstudios.com. It allows you to have AIM/MSN/YAHOO/MIRC/ICQ all in the one program as oppossed to many different ones.
It has its quirks, trillian does, but overall its not to bad. Just a suggestion.
Good Luck!