What does the error mean? I am unsure. Most likely it is a problem with the program. Norton for Mac has a tendancy to crash when it can't fix a problem. My second guess may be your hard drive is failing, but it is much more likely a problem with Norton.
How to fix the error? There may be a couple of solutions. The first one I would try is updating 8.0 to 8.1, as 8.0 is not actually "certifiably" compatible with Panther (10.3.x as you mentioned).
The second one would be to boot from the Norton CD, rather than run it under Panther. Even though it is incompatible with Panther, Panther uses the exact same file system Apple has been using for years. So Norton 8.0 willl work fine as long as it is loaded in its own environment off of the bootable CD. You can boot from the CD by loading it into your optical drive, restarting the computer and holding down the C key after the chime.
You know, I've seen a lot of Norton Utilities related problems on Macintosh. It seems to have a fairly loyal base of Apple fans who swear by it, but it really isn't something I'd put a lot of faith in. The Mac OS Extended file system is fully journaled and has a pretty minimal amount of problems short of disk failure. Norton's disk utility really isn't necessary to run and can actually cause a whole host of other problems with its "iffy" solutions for fixing problems on your Mac. I've seen some instances where Norton would render an installation of OSX unbootable, cause problems in startup or cause some programs not to work anymore. And the program itself has a tendancy to crash when it has the slightest hiccup...
Just a warning of course. Like any utility, it can save and destroy.
