Snow screen effect?

this really confuses me. i believe its a problem with the av chip but every time i play certain games lets say Halo 3 for example, the menus look fine then once a map is loaded i get a blocky, grainy, snow-looking effect. has anyone ran into this problem before? much advice would be appreciated since i dont really want to send my xbox in for 3 months or so.

sometimes it will be a blocky grain pattern going on like on red faction: guerillia everything looks fine except the sky is just filled with this grain effect. ive tried multiple av cables and hdmi cables on different tvs and it still is the same. but its not so bad on some games where its there but i can live with it.

yea ill probably do that, just wanted to see what the community knew before i called them and have to send my xbox out for about 3 months haha

i know what it is cause i had that twice, e 74 error

Well it might be e 74. I never got a snow screen effect but my whole screen did turn black and white if I remember correctlyPuddinPant