I had the same problem. It started when my definition subscription had to be renewed. I chose to buy the updates for NAV2004 for another year. When I purchased the renewal, I downloaded the new updates and got the same error message. I tried everything Symantec recommended and nothing worked. I sent Symantec a nasty email and they said to update to NAV2006. I purchased the 2006 download and installed it,but got the same stupid error message. I chatted online with a Symantec technician. He said the problem was Norton Internet Security 2004. I removed NAV, but didn't remove NIS. When I removed all the Norton programs and installed the new NAV 2006, everything worked. Hope this helps.