I'm an AD newbie (and loving it so far) but I had my first beta crash today :) I had closed Designer with the help page open and when I tried to run Designer again, it crashed with this message:
An Unhandled Exception has occurred. Code: 0x80070079
It happened a couple of times before I spotted the help window was still open and closed it. It loaded fine after I closed help and then started Designer.
I'm not having trouble making it crash if I do the above, so hopefully it's an easy bug to squish.