I had the exact same problem and was told by MS that the SQLVDI.dll was throwing these errors but that my
SQL2000 and SQL2005 instances were working and backing up properly. I was told that I could safely ignore these messages. They said a hotfix may be available about the middle of next month and that I could call then to get it. They also said that the fix would be in the next/future rollup.
What other problems/symptoms are you having?