Picture's going through from all sources (PS3, X360, DVD player), but no sound. Happened last night as I paused a movie on Netflix...came back and suddenly there was no sound. Tried it again about an hour later, got about thirty seconds of sound and then it winked out again - still, with a just-fine picture.
This morning I tried the TEST button - instead of cycling through all the speakers with a tone, it cycled through each of them with static. I unplugged and replugged all HDMI, restarted the whole thing, and just as it fired up the picture from the PS3 (after some time of seeming unsure about what it was getting) I got about a half second of deafeningly loud foghorn noise from the centre speaker. Still no actual, useful sound.
So I tried TESTing again and it thinks it's doing it, but I don't even get the static. The display on the front of the device thinks it's getting and sending 7.1 sound.
This thing's about 5 years old, it's served me well in that time but it won't kill me to replace it, I just don't want to if I don't have to.