Yes I am(HDMI), but I also have analog ins from the same STB so as to have video record in/out and zone 2 capabilities(HDMI can't downconvert to 480i).
These extra inputs may be making the Denon hiccup while it processes the signal? I never tried it without the alalog ins. The one advantage with analog ins simultaneously is that when you switch to menu funtion, it displays the menu over active picture(although downrezzed to analog and I guess re digitized to pass thru HDMI. With HDMI in and out only, it displays the menu over a black screen.
Ps. Despite my harping on the BluRay DVD fiasco, I succumbed to the walmart secret sale this morning and bought a Toshiba HDA2 for a price that once I get the 5 rebate movies will be free for all practical purposes. With this as my second HDMI input to the Denon, I'll be able to compare and see if any sync issues happen. I'm thinking its the analog to digital changes.