Sorry for your problem. Your first mistake was using Norton at all, the product has been
discontinued. Norton Utilities was discontinued because it cause so much problem for OS X I wish I could speak French to make this clear to you).
I will try a least of possible fixes:
1) Go to Applications->Utilites->Disk Utility and highlight your drive and click "Repair Permissions".
2)
NEVER use again Norton Utilities again for the health of your system. You should consider a product called
DiskWarrior.
3) Zammy-Sam's suggestion of trashing your com.apple.finder.plist in your Users->Your Username->Library->Preferences is good.
4) If none of that helps, boot the computer with you OS X install disk, when the install program starts up, go to the Menu and Run Disk Utility and Repair your startup drive. After that reboot your machine from the hard drive.
5) If nothing above helps, then consider to reinstall the
OS X 10.3.4 Combined Update. After that is done then re-run Software Update.
Good Luck. There are some users here that speak French. Hopefully they will come to this thread.