Xbox 360 suddenly pixelated?

So i was playing gta 5 on my 360 and noticed how bad the resolution had become (didn't notice before because i was playing minecraft lol) anyway all the sudden my 360 has gotten pixelated… Not AS bad as if you try and use the standard RCA xbox cables. But pretty bad… This happened after getting back online with it after a long time of not having it hooked up to the internet… It downloaded a microsoft update, then my 360 got all pixely. I've tried EVERYTHING… Tv settings. Xbox setting display settings. And nothing will fix it. I have to remind myself it wasn't like this before. And i never changed anything:/ my xbox was fine on my tv. Perfect picture. Updated. Boom. HUGE change in the resolution. In games. At the title screen. Everything. Maybe its just hardware? Video card going out? But there's still the coincidence that it happened RIGHT after the xbox update… ANYWAY… Long story short. My xbox updated. Now my graphics are dumbed down to looking like a pc game on 800x600 resolution… Does anyone know ANYTHING about this?