Alan, is only one tuner or both tuners are connected to ur box.

if only one, is the second tuner configured as loopthrough or u selected "not connected"

if it is only one then the second channel u'll be allowed to watch will be limited as per the first selected. if u go through the channel list, u shall find not all channels are greyed out but still some are in white and so u can select.

to fully eliminate this and to see two channels independently u need to have both tuners connected if not already.