It is definitely an intermittant issue with my setup--HDMI from HR21 to Sony Bravia and digital optical out to my Sunfire AV preamp. For example last spring, House was virtually unwatchable in DD through my surround sound speakers, the lip synch was so far out of whack. This fall, no such issue with House, but I still see it on my Fox station--example, during the Sunday football game when they show Troy Aikman and Joe Buck talking in the booth, they're way out of synch. But the football sounds (hits, crowd noise, thunk of the football being kicked) are not out of synch or if they are you don't notice it.
Through the Bravia's on board speakers lip synch is fine, and that's how I watch TV when I see glaring lip synch issues.
Unless it is every station and show, being able to set the delay in an AV receiver is little help as it is a moving target. My Sunfire is fairly old and does not have that capability in any event.
If your AV receiver can pass HiDef via component or HDMI to your TV, you might want to try connecting the HR21 video and audio to the AV receiver, and then run component or HDMI to the TV to see if the picture is in synch with the sound coming out of the surround sound speakers.