Monitor 1080p weird problem

[shades1]

I'm using an acer 22' p223w w/hdcp support. I'm also using a dvi to hdmi. All the display modes work fine except the 1080i. The 720p looks great but when I tried out 1080p it looked even better and now I don't want to switch back to the 720p . But the problem is when I turn the 1080p setting on the ps3, I get a little box floating around the screen, saying "input not supported" even though I can see the picture much clearly. I tried playing a blueray it displays it clear, didn't try it on a game yet. Only problem is that floating box thing and it goes away when I put it back to 720p. Anyone have any ideas how to fix this weird problem or how to remove that annoying box floating around?