I have a Sony BDP-S370 Blu-ray player I bought a few years ago. It is essentially new as it has literally only been used once or twice. It is connected to a Sony KDL-50W670A TV. Both devices work fine and picture quality is good, but today I was playing with the blu-ray and I noticed that it was 1080i, not 1080p. Since both devices are capable of 1080p, I got to wondering if a setting might be wrong and decided to check.

No problem with the TV, it displays full 1080p with other sources. I checked the player, which was set to auto. I changed that to 1080p and the display started flashing. I put it back to 1080i and everything was okay again.

Can someone explain what is wrong with this picture? Both devices are supposed to be 1080p capable, and the TV has no problem with other sources, but the Blu-ray produces a flashing screen if set to 1080p and only works correctly if set to 1080i. Am I missing something here?