I have bought Xbox 360 Slim 4Gb 4 days ago. And yesterday i had a problem with video. I've used HDMI to DVI cable for 1080p resolution on my monitor, which worked fine. I have played standard game - Phelix HD or something called like this. Then i removed the cable from my monitor, and plugged my pc cable there. After 1 hour, Xbox turned off, then i put back cable for Xbox into monitor, and started It. And at startup there were flashing yellow dots all over the screen, nothing helped till now.
Only 720p resolution works fine without flashing dots. 420p has a lot of dots, and 1080p smaller.
I don't know how that would happen... And how to fix it...
Take my xbox back to store, to repair it. Or try another cable ?
More about :xbox 360 slim 4gb 1080p 420p problem flashing dots
I have bought another Cable, to connect my XBOX to TV, and set resolution on it to 1080p and it works fine. So problems was in HDMI to DVI cable. It worked only 3 days normally for me So... be careful everyone when choosing HDMI to DVI cable, don't buy cheap cables. Good Luck !