i think thats the problem with the rockchip, its fixable if you play around the video conversion.
All rockchip players that currently use the R2608A chip will play the video find, but almost ever 5 - 8mins will loose lipsync for about 30secs before it goes back to normal.
If you reduce the quality of the video (say from 24fps to 20fps), then you will see this lip sync problem much less.
Again I hate to oversell this. But, on my Oppo Rockchip player I watch FLV video alot. I watch a lot of hour long documentaries from the BBC, and I have converted 3 films (TMNT, Spinal Tap, The Mummy Returns) each around 1.5-2hours long, and the audio is always in sync with no issues.
I do not want to keep jumping in with this same statement, but with rockchip players its all about the conversion. I would suggest that people dumb down the audio to mono and low bitrate when watching video. This can do wonders for your video experience.