Yes, I agree that it's problematic. It wasn't actually all at once but for purposes of this problem wasn't spaced enough apart to have given me any data since I didn't experience the first hang (at least not the first one I recognized) until everything was updated. The actual time frame was a couple months with the guest being first, then Ubuntu, then workstation but that doesn't help. I may try Debian at some point as well but I think just a mainline kernel and serial console to get more info is up next. At least it'll no longer happen when I'm away since I've disabled automatic Win updates.
I should probably have mentioned above that there are no log entries of any sort after the hang. For the ones that have happened in the wee hours, the logs after a reboot later in the morning all end at the hang (i.e., no further kernel logs, daemon logs that would otherwise occur constantly from the firewalls, dhcp daemons, etc.). I'm not sure whether the kernel is never printing anything or whether it's just not making it to the file system but the serial console and a log of that will hopefully answer that.
Jeff