Did this just start happening on 1/24?
We started to have disk resources go offline on a Server 2008 failover cluster on 1/24 at about 1pm EST. We are using 8.7i patch 2. I have since disabled 8.7i to see if the behavior persists. There had been no change in policy configuration in our setup -- the only change would have been updated DATs.
VirusScan Enterprise Product Version 188.8.131.520.Srv
Hotfix/Patch Version 2
DAT Version 6236.0000
Engine Version 5400.1158
Engine (x64) Version 5400.1158