What is it? Display or GFX-Card?

[timbuk2]

Hello,

Got this rather strange display-errors after 1 week of vacation on my 27" mid-2011 imac.
Is this a Display error or is it the gfx-card?

It's not a static image. There is some strange flickering and different Images...
See The Screenshots.

Thank you for your hints

 

[redheeler]

Looks like the GPU is beginning to fail. The 27" 2011s are known to have defective GPUs, so much so that Apple even set up a replacement program. See this article:

http://support.apple.com/en-us/HT203787