I don't have any third party AV, so I don't think that's part of the problem.
I have a brand new MacBook Air, installed Windows 7, and everything was fine until the first Windows update. After that, I could not boot into Windows, although I could boot into the Mac side just fine. My crash occurred at classpnp.sys
Rolling back to an earlier save point "fixed" the situation. However, as soon as Windows noticed that it did not have the update, it downloaded and installed it again and I got the same crash. So now I have disabled Windows updates and things are stable.
I did take this to the Apple store tech supprot (Genius Bar). After waiting an hour to be seen, I was told that they know nothing about Windows and it was not their problem. The suggestion was that I call Microsoft, which is just silly.
If anyone figures out how to update, please post.