If you read what it says on the resolution selection screen. It's like this
480P - Check this if your TV is only capable of displaying 480P
720P - Check this if your TV is only capable of displaying 720P
1080i - Check this if your TV is capable of displaying 1080i
So that makes it sound as if your TV CAN run 1080i, then you should. Anywho, who do you know what resolution channels are outputing?