HDMI resolution problems

[dearfred]

I have a Dish 921 DVR hooked to my Panasonic 42" plasma.

I could not get a full screen on non HD channels- not matter how I adjust either the resolution on TV or 921-

Then this morning-- it worked fine- The screen was full- I didnt do anything

I rebooted the 921 dvr- and now can not get it again to Full screen-

Any ideas?