This is not a sync problem of any kind, as it is reproducible without compiz. This is a rendering problem.
The libcairo people insist that this is a very specific nvidia driver issue:
The murrine people has narrowed down the part of libcairo which triggers the nvidia problem:
This issue means that with the new cairo, which is going to be used by all linux distributions, the nvidia driver will render all themes, save the most ancient, sluggish and ugly. I would really like to know if the nvidia developers recognise this as a problem.