I suppose you run 12.10 natively, ie with unity-3d and Compiz. Whereas 12.04 in a VM will default to unity-2d which is using another window manager (not compiz) which does not exhibit the issue.
I suppose you run 12.10 natively, ie with unity-3d and Compiz. Whereas 12.04 in a VM will default to unity-2d which is using another window manager (not compiz) which does not exhibit the issue.