I've had similar problems in HD in general also, not just with NFL. On my received (622), there is a setup option to sync the sound with picture for either HD or SD. I picked HD option and it seemed to work.
This is a known issue with most transmissions, since the sound is sent along landlines then transmitted to the satellites and then received by us. Landline transmission is always delayed by a few milliseconds (cheaper because of low bandwith requirements) and after all the repeaters it had to go through, the delay adds up to be noticable at the receiver end.
Sometimes I get almost .25 seconds of audio delay. It looks funny because the persons lip stopped moving and the sound is still coming from them.