My experience with Avantgo (updated only through hotsync), is that two things (perhaps in combination) lead to crashes. First leaving Avantgo on the screen and closing the flip. This frequently hangs the phone. Also, losing reception (red light flashing) while Avantgo is running can lead the a hang of the Palm. If I always exit to the launcher before closing the flip, I end up with very few crashes.

-Stew