Get this – that doesn’t work yet!  I had the same error as popped up in this thread and evidently the work arounds are not too pretty.  Word to wise is to create an R2 VM on the virtualization platform you want to be using.

It appears, reading through the release notes for vSphere 4U1 that 7 and R2 are at least officially supported operating systems now.   So get right on that vCenter update, then your vSphere server updates.  You know the drill!  At least these should be the last significant OS releases from Redmond for a couple years 🙂

–Nat