Sound stopped working. Win 7 guest on Win 7 host.

[MyBrainHurts]

After a power outage, I can no longer hear anything from my guest VM's.

The sound works on the host, the mic on the headphones work on the host. The sound and mic does not work on either of the guests. I've reinstalled Virtualbox, I've tried the Intel HD audio driver as well as the AC97 driver. I've reinstalled the recommended sound driver on the host. Nothing restores the sound. I have verified multiple times that nothing is set to be muted on either system.

Does anyone have any other suggestions?