I've had similar problems with updates from Internet Security 2003 to 2006. I decided that life was too short to struggle endlessly, talking to India for support, obtained a refund from Symantec, installed AVG and Spyware Doctor, and haven't had any problems since.

I had used Norton for years, but had become increasingly fed up with the overhead and the slowness of the updates, so the change has been welcome.

Alan