The fix for this is actually way simpler than you think.
When you turn the TV back on and see MCE loaded in 4:3 mode, leave it on! Instead go to Tasks > Settings > Display and re-configure the monitor in THERE to be 16:9 with whatever the proper 1080p resolution you want.
Then everything should work perfect from that point forward. I had the same issue with my Onkyo receiver and my HTPC on turn off/on of the display.
