I just purchased an M1 and I'm getting the same message, "unsupported signal", for 1080 channels. If I switch my DVR to 720 it works. I bought the M1 because I though it would work with 1080. Is it possible that the component cables connected to the Slingbox do not support 1080? I'm going to fiddle with it tonight and I'll post a reply if I find out anything.