something changed in the kvm audio subsystem, so a virt that was suspended during shutdown wouldn't resume after reboot. the logs had complaints of:
savevm: unsupported version 2 for 'hda-audio' v1 load of migration failed
i poked around on the rh bz site and found a few hits, but they seemed to be related to older versions. i forced a clean boot of my vm and it was happy.