Just wondering if this sounds familiar.
I installed updates this morning and rebooted to get the latest kernel-3.8.9-200.fc18.x86_64 running.
I'm using HDMI audio by default and it was working fine for a few hours then suddenly stopped.
I turned on my receiver and switched to SPDIF output, and had sound again, so parts of the sound system were working OK. I tried switching back to HDMI and "Test Speakers" made a rude noise once, but never played the test sound, so I switched to SPDIF again.
About an hour later, I tried HDMI once more and it was now working flawlessly.
There were no messages in any logs I could find about anything happening to audio.
Just another in the strange happenings since I started using 3.8 kernels...