An unrooted NC plays my AutoGk 480p rips in the built in player if you remux it into an .mp4 file with AAC audio.
This is something most people don't realize you can do. The video stream in an xvid/divx avi CAN be read by most mp4-friendly devi...
If the audio is dieing after the device goes to sleep, this appears to be a defect in certain batches. I had this problem (even after hard resets), but exchanging it out for another took care of it for me.