The output to 1080p via mini-DVI has started to display corrupted video output then the audio which I'm running over USB starts sounding corrupted. My screen splits into 2. Jagged.
You should be able to get the GPU fixed (logic board replacement) through Feb of 2016 under the terms of the AppleCare extension. Check with your nearest Apple store. Only option if you want to keep the 17" screen.