Hey folks, just got notified to update my Catalyst for my ATI Radeon HD5700 series so I did (Version 12.4 Dated 4/29/2012). Interesting problem popped up right afterwards. My card is attached to my flat screen TV (I'm using the PC as a media center) via an HDMI cable. When I turn my TV off for the night and back on again in the morning, I have no audio from the PC over the HDMI cable! The audio properties show the HDMI cable to be unplugged but clearly it's not since I'm reading it on the screen. If I unplug and plug the HDMI cable back in, voila! Sound is back. I have to re-seat the cable for this to recover, I've tried disabling and enabling the device, defaulting to external speakers via RCA cables into the motherboard etc....cable has to be unplugged and plugged back in again. It's not the flat screen, I tried using different HDMI ports on it (I've got 3) and my PS3 and whatnot run just fine with all 3 ports. It's not the Radeon hardware, the video and sound work just fine after re-seating the cable. The problem started immediately after your last driver update so I'm quite sure that's where the problem lies. I believe it's some kind of "sleep" issue?? In another words, for some reason when the external HDMI receiver powers off, Catalyst now treats that as "unplugged" and only the audio cannot recover properly when the device powers back on. Take a peek please and let me know what you find.
