Sequencing is typically what makes HDCP compliance get out of whack, especially if one device is a bit quirky in its HDCP implementation. My Pace HD box's DVI output is very fussy about HDCP - even when directly connected to the TV. Is the 990 switched to the cable box's input when you turn the TV on? The Gefen would always be in one of two positions, and might have already been switched to an active DVI source typically when you powered up the TV - the 990 wouldn't send anything to the DVI output if it hadn't already been switched to a DVI source, which could be what's upsetting your TV.