Yes, this is Vista only and quite frankly I don't consider it a problem. It's a built in behaviour and can happen for a number of different reasons as explained here:
http://windowshelp.microsoft.com/Win...a017c1033.mspx
So I'd mark this as "not a bug" and leave it at that. Perhaps an entry should be made in a FAQ somewhere since I'm sure at least a few questions will be curbed before taking up someones time that way.