I’ve had difficuly syncing audio and video when working with large HD comps.. seems that the audio plays on at normal speed, even if the fps on the video lags behind. Causes some real headaches when trying to sync VO and supers.
Skipping 1 frame on the ram preview seemed to solve that problem for me. Can save a lot of time too.
I don’t know if that’s causing your problem, but it’s worth a shot.