I've had some random behaviour in this regard; I used to have similar sounding crash-no-way-to-restart hangs on 8 and 8.5 actually. I found at one point that it was leaving garbage in memory that was not getting cleared, and had a shortcut to a kind of force-clear-all-unused-memory command (I forget what it was exactly) on the desktop. That would work, though sometimes I had to do the task-manager kill process thing as well to get rolling again. Maybe helpful? (This is all on XP mind you, with an E-mu 1616m sound card).
Since X1 I have had none of that, very occasional crashes that require the task-manager trick but nothing worse. I have found it pretty solid. This is a relatively old machine (2007 I think) and has had a lot of heavy use, and it still ploughs along pretty well under XP/X1. I don't know if it will run X2 yet, might need to finally move up to Win7 (or 8?).
I have had issues on my Win7 laptop, the worst was using Asio4all with onboard sound (in a pinch, on a plane), I had constant crashing that was driving me crazy until I figured out it was a particular *patch* in a particular Reaktor ensemble - not the ensemble, which would run other patches just fine, it was literally only that snapshot that was killing Sonar. I froze the track and suddenly, smooth sailing. Weird.