I switched mine to sd sync and my lip synch problems went away on my 722. That and I have an audio synchronization feature on my Sony A/v receiver and it is set to 2 which gets me in synch on both tv and a/v .
I get it a lot on my local NBC over the satellite, but not OTA. I also had it bad yesterday on the new HistoryHD, never cleared up, and many others complained about it. It happens on MonstersHD sporadically.