Believe I was responding to a different person with the opposite, and more frequent, problem.
When video gets ahead of the audio that's rarer and I have seen it before on other setups - this means something in your chain is causing lag. The most notorius setup for seeing this in is when you use a dual hdmi out on say your bluray player and the video goes direct to the TV but the audio has to travel to a receiver and then get decoded. If this is your setup then its a good idea to try having your Bluray player do the decoding (dolby digital etc.) and have it transmit out to your AVR via PCM. Or if possible just have the video go through the AVR and then on to the TV for that source.
What does your setup and connections look like?