My 811 ota guide just quit displaying my local NBC digital off air chanel. I went to add DTV in the menu and was successful in restoring it. My signal strength on this station is above 90%. Is this common or is there something I can do to keep this from happening? Also, every night I power off the unit but when I turn it on the next day it has to download the program guide. What gives, my 501 doesn't behave this way. Anyone have any suggestions? Thanks in advance.