The picture quality on my 60" Sony LCoS is suddenly lousy recently - just muddy and fuzzy, like watching a standard dvd. It seems to only be this way when watching comcast digital cable channels, including HD channels. is there any sort of check or anything I can do on my comcast cable box to see if it's the fault of the cable box?

yup, Comcast dropped the ball..

http://www.avsforum.com/avs-vb/showthread.php?t=1008271