Notes 8.5 crashes my O/S (Win Vista Business 64 bit)

I’ve got Notes 8.5 running on my new Windows Vista (64-bit) Dell Precision M6400 - I know it is not supported, but at least it works reasonably well!

My problem is that every time I quit Notes, it freezes the Operating System as well. The same goes for Sametime 8.0.2 (stand alone), whenever I go into “Preferences/Telephony, Audio and Video”. Since it is the same behaviour for both Sametime and Lotus Notes I guess it has something to do with the JVM (?), but how do I really find out what is causing this crash and is there a way of fixing it?

Is anybody else seeing the same behaviour, or is it something with the installation of my O/S that is the problem?

Sorry - wrong forum - cross posted in R8.5 forum as well.