Just ran into an issue in the lab and was wondering if others ran into the same issue. Basically, I just upgraded from U2 to 4.1. I setup a new VCenter server with 4.1 and then upgraded the hosts to 4.1 after. No problems at all really. The issue came up when I realized VDR stopped backing up my VCenter server and domain controller running Windows 2008 R2. Both had the same error regarding quiescing a snap. After some research, I ended up removing the VSS support drivers installed with VMTools. After that, snapshots for both worked fine. Since they were both VMTools upgrades from U2, I tried to uninstall and then reinstall VMTools from scratch. It still broke the ability to snap using VSS. It only works when I remove the VSS support drivers. Now it does not seem to be a Windows 2008 R2 issue necessarily as a generic 2008 R2 server snaps fine. It's just ones that seem to house AD or AD LDS. Also, when I was on 4.0, 4.0 U1, 4.0 U2 I did not have problems like this. Anyone else run into this?