I have a lot of recorded TV Shows that I recorded with another DVR program and transcoded to H.264 .mp4 files.  When I try to play these in Media Center, either from the video library or from Media Browser the audio ends up being off by about half a second.  Sometimes I can see the video stutter when it starts up, which might be contributing to the audio sync option. 

 Skipping forward or backward within the file doesn't help, neither does restarting, the issue occurs consistently.

 The bit rates are fairly low, they're compressed to 720p with 2.5 Mbps average bitrate.  Audio is 192 kbps.

 Any ideas what the problem might be?

 I should have mentioned that these files play back fine in Beyond TV (the software that recorded/transcoded them) along with VLC, MPC-HC and anything else I've tried (now I need to try WMP since I don't remember if I've done that...)

I found a solution to my problem.  I spent a lot of time messing with DirectShow filters to try to get Media Center to use a different codec to play back the files.  It turns out I needed to disable Media Foundation to get this to work.    I used the tool from here to do that: http://forum.doom9.org/showthread.php?t=146910

Now my .mp4 files have proper audio sync in Media Center and Windows Media Player.

Be careful playing around manually with Media Foundation. In fixing one thing, you might break something else!
Win7 MC (& MP) has a fairly common playback sync problem with certain media files. Microsoft really should look into it !?!

But anyway, I have had my HTPC for about 6 years. Started with XP, then Vista, both of which didn't have native support for a lot of formats. I always installed the Shark007.net codec pack for trouble free playback.

With Windows 7 I tried to go without it (because its supposed to have native support for most formats) but ran into constant sync problems. Today I installed the Shark007 Windows 7 Codecs (http://shark007.net/win7codecs.html) and now they are perfect.
Have a read through the link above. The Settings Application included is fairly complicated, but I didn't need to touch any settings in there. For me a default installation did the trick.
I've just tested it with a few avi's for now, but thats good enough for the time being. I'm pretty sure if you run into problems with other file types, you can use the Settings Application to choose different splitters and decoders for specific filetypes.

 Thanks for the warning.   So far so good, though.