cfrieler, What happens if you try to update the definitions using the Intelligent Updater? (Look for 20101008-004-i32.exe or -i64.exe if a 64 bit machine.)
Unfortunately, product updates for SAV never come down through LiveUpdate. I feel your pain for the process that you have to go through to get upgraded, but it's only fair to mention that not only is the version you're showing, 10.0.1.1000, an old build, but one for which security vulnerabilities have been identified; 10.1.9 (MR9) is the latest available build for SAV.
Rudolf, are your clients checking to Symantec LiveUpdate server, or an internal LiveUpdate server? If the latter, ensure THAT server is up to date.
sandra