My point was trying to test the 30' cable. So, let's try this. Connect the 30' cable from the DirecTV box to the TV. No scaler, no receiver, nothing but satellite receiver, 30' cable and TV. Set the DirecTV receiver to 1080i first (you'll probably have to uncheck 720p and 1080p) and see if that works. If it works, then select 1080p. See if that works.
If both work, then your cable is probably fine. If 1080i works but 1080p doesn't, then you probably need a better cable. If neither work, then you have a bad cable.
If both work, then you can add the receiver next. If that works then add the scaler. etc etc. Add one thing at a time to try to pin down the source of the problem.