Strange -- after installing the new kernel 3.9-6.towo.1, and rebooting, the system came up with no sound, and no audio devices except the connected USB webcam. aplay -l showed no sound card. dmesg showed many many errors of all kinds.
So I rebooted to watch messages, and the second time the system came up perfectly with no errors, and sound is working perfectly. dmesg shows no errors, and only a couple of old ACPI warnings that don't mean anything.
Poltergeist!