After recently transitioning to client side targeting two of my servers - both 2008 R2, built around the same time from the same VM template - are having difficulties remaining in their assigned groups.
Both servers will temporarily show up in WSUS (in the desired group as well as the all computer view) but not at the same time. Both boxes are domain joined and not experiencing any other problems so I don't think the problem is with the box GUID.
It sounds like an issue of having one account object being shared between both systems but I have no idea how that could have happened or how to correct it. I have looked in detail of the windowsupdate.log on both systems as well as our WSUS box.
EDIT - the behavior is a lot like having one account shared between both systems.. While one is actively using WSUS the other can not be and visa versa.