[ashlar]

...the lipsync issue is only present when the missed counter runaway increments (press o during playback).

The missed counter seems to always increment after pause/resume or rewind/fastforward or at the start of initial playback - but to stop it runaway incrementing I just skip back or forwards (left/right arrows key) 30 seconds. I've found for this to work you mostly have to skip back and forth a few times before the missed counter stops incrementing.

So, I think you can use the missed counter as a guide to whether the lipsync issue is occuring/going to occur shortly.

With the above settings I'm able to playback 23.976 movies with no issue with lipsync - just remembering to skip back at the start of the movie and after any pause/resume or rewind/fastforward.

In my case, the missed counter runaway increments happen pretty much at every first video I watch after resuming from standby and relaunching XBMC. If I stop and play the same video, no runaway increments. It seems pretty constant in this regard. Gotham Beta 2, Win7 x64, Q9550S, 8GB RAM, GTX660 with latest drivers from Nvidia, audio HDMI from the GTX660.