Has anybody had the game hang on a unit during a long campaign battle? By that I mean sometime during the middle of a turn after I move or fire a unit that unit stays selected no matter what other unit I click on or anything else I try to do to deselect that unit. I have been playing the long campaign as the Germans and have had it happen to me twice. I am playing the Version 3.0 download version on a Windows Vista machine and haven't had any problems other than this that I know of.
That has never been reported by anyone in the 10 odds years of SP, that I can recall.
Therefore I would tend to suspect something that you have running on your machine or the Vista operating system, which is not an officially supported O/S.