Paul, Running on W7-64 I had a freeze and an Access violation error after using it for a couple of days but I did not take a note of it and can't actually remember what I was doing in biab at the time, something with chords I think. However once I closed with the task manager and re-booted everything was fine and have not has another since. I remember it happened a few times when I first got version 10.5 too, maybe updates have sorted it out.
I don't fancy turning off UAC as I use the system for many other things other than music.
Jeff