After connecting my PC monitor cable to our Sharp HDTV mod. #46SB57U, I couldn't get it to work. When I tried to tab down to #-4 PC mode, the select button would skip past and go to #-5. I also noticed that the #-4 symbol was faded, as if to indicate that it was unavailable. How can I correct this problem so I can connect my computer to this TV? Thank you very much,