My Slingbox Classic worked great with my old Comcast DVR, but not with the new X1 box. I'm connecting with a composite cable (red, white and yellow outputs from the DVR and a single 3-layer input to the Sling). The sound works fine, but there's no video. Just a blue box that says "weak or no video signal." The video resolution is set to 1080i. What should I try? Has the old Classic finally become obsolete? It has been such a workhorse, I hate to give up on it.