Hi, Neil. Given that what you've done has eliminated the error codes, it may may be worthwhile trying the Norton Remove and Reinstall Tool again, to make sure the copy you have is not corruped in other ways.
As always, run Live Update after, until no more are found. Also a reboot after may help, too
Let us know if that works. If not, we may be able to get someone else from Symantec to look at your problem.