I am just posting this here in case you don't follow me on twitter and happen to have this issue.
Alright so a weird one tonight, basically I have tons of m2ts and avi files which just have AC3 audio usually in them, or even lesser in the avi. I had no issues playing these files on my Windows 7 HTPC or even my Windows 8 laptop. However I recently wiped the win7 htpc and installed WIndows 8 Pro with Media Center. Now ALL of my Live and Recorded TV works just fine, but when I try to play back these ripped files WMC just says can not open file and Media Player throws error C00D11B1. Now Microsoft has a help page that says that you should upgrade your sound drivers, but I did that and still the same issue. I thought maybe it was a network permissions thing, so I installed VLC and it played the files just fine. Sooo weird. SO I tracked down differently people with this problem and it seemed random, and I tried just about everything and then I ran across a secrete registry setting pertaining to DRM that will solve this issue for you.
1. Hit windows key or go to metro and type regedit to bring up Registry Edit
2. Go to: HKEY_LOCAL_MACHINE/Software/Microsoft/Windows/CurrentVersion/Audio
3. Edit or Add DWORD “DisableProtectedAudioDG” appearing in the right window.Enter 0 or change number 1 into 0.
4. Close registry and restart your PC.
It is very important to restart PC. after all of this for it to work. Live tv, recorded tv, and all my files play now! Very strange. I am pretty sure it isn't restricted to Windows 8 and is just some oddity.