I'd check that cable box manual and see what happens on the different modes. I'd also check your receiver manual to see what happens with the differnt modes and the input mode signal.

Some times these interactions get a little complicated.

The Rat. M80s, VP-150, QS8s, SVS PC 20-39+, OPPO, Onkyo 703s, Harmony 880 Sony 60" SXRD HDTV