Did you remove SP2?
That fixed it for me.  I wiped the system and re-installed.  I turned off Vista updates so that my HTPC no longer gets any update notices.
For my specific hardware I also installed the latest HDMI Audio driver from Intel instead of the ASUS motherboard driver and that fixed the intermittent sound device auto-detect PnP issue.
IMHO if everything works fine pre-SP2 there is no real reason to install the update on a dedicated HTPC.

Yes I removed SP2 and everything is working fine again. I also turned off updates for Vista. Tried several different audio drivers with SP2 to no avail. My only concern, what if MS adds functionality to MC that requires SP2?

I just changed the audio output device and it fixed it. No new drivers or anything... Using ATI video card for HDMI and Realtek for audio.

SP2 messed up the playback (stopping at end) of video in Media Center and unstalling it was the only fix. I have turned off auto updates and will never upgrade again! Forget W7, I'm not taking any chances on buggy upgrades since Vista SP1 seems to be OK.

rhino8005:

My only concern, what if MS adds functionality to MC that requires SP2?

If they don't fix the SP2 sound & freezeframe issues then any new MC functionality would be useless to those people having the issues.  :-/

chrisaroz:

I just changed the audio output device and it fixed it. No new drivers or anything...

Unfortunately that won't work for everyone...  :-/
In my situation my HTPC has three sound devices (Realtek HiDef & SPDIF and Intel HDMI) and the one I was always losing was the HMDI audio.  Which I couldn't do without.  So I had to do the non-SP2 setup in order to keep that running.  Sure I probably could have gone with using the Realtek SPDIF out to the surround system but I don't always have that turned on -- and most of all, it should work regardless, and the bug is MS's and I shouldn't have to hack around it.  :-)

Danno:

Forget W7, I'm not taking any chances on buggy upgrades ...

I'm running W7RC on another system (not my HTPC) and so far I like it better than Vista, but I haven't put the OS through all of its paces yet.

ok guys this is the fisrttime i have used a forum , please forgive me if this appears in the wrong spot

I had no audio with Realtek HD Audio when i installed sp2. I found a solution that worked for me.
go to realtek hd manager in control panel , click speakers configuration , on the right hand side you will see "analog back panel". double click the little grey plug and then select "front speaker out".

Click test and you should have all your sound. I worked for me , but i dont know much about computers so it might be different, but this is the forum i found to try and resolve this problem.

SP2 working fine with audio now. let me know how you go guys , I hope i was of some help. Thankyou.

Good find, thanks for the post (and welcome!)

Welcome!

Couldn't make this work. To recap:
* I have Realtek HD w/HDMI + Creative X-Fi
* Pre-SP2 all audio worked with no issues
* Post-SP2 regular audio still works, but no Dolby Digital (e.g., Media Center CableCard recordings) through HDMI using Realtek drivers (using X-Fi SPDIF still works)

I tried all the things suggested in this thread to no avail. Here is the issues I ran into with this recent suggestion: I installed the latest Realtek HD Driver (July 2009), but I don't have a "Related HD Manager" per se -- all I have is the standard Windows Sound Control Panel UI. I see Realtek HDMI listed in there, but there is no little grey plug to double click. In the Window I see three entries: Realtek HDMI, Speakers, Creative X-Fi -- exploring each one and their properties no little grey men - errrr - plug.

The only solution that kind of works for me (while under SP2) is to uninstall Realtek Driver from "Uninstall Programs" BEFORE REBOOTING go to device manager, re-scan and install the default Microsoft Sound Driver. That way I DO HAVE regular + Dolby Digital audio through HDMI under SP2. The only issue is that once in a while I get a very loud hiss (once or twice a week). If that is not odd I don't know what is.