There is currently a problem with the AV definition update for the older AV engine that is in 8.8 SP3 and older versions of Management Suite. It is being worked on by Engineering. If you update your clients to the new AV engine in SP4 it will work.
If you update your content, this should work now - we should have it resolved on our end.
- Paul Hoffmann
LANDesk EMEA Technical Lead