I've downloaded this example of Video Texture with synced sound on

http://blenderartists.org/forum/showthread.php?t=178877

I tried the example with 3 computers:
- one running windows vista professional 32bit
- one running windows 7 professional 64bit
- one running windows vista business 64bit

In every case the example plays well (both audio and video) with the latest 32bit official release of blender 2.5 alpha 2, both in 32 and 64bit operating systems.

The 64 bit build does not play the video well and the sound is skippy.

At the moment I'm not able to test it with a linux machine, but I will try it soon.

I've attached the .blend file that you can find in the aforementioned thread, the video is the big buck bunny trailer.