Colorful squares appearing at my screen

[VMMichel]

Hello,

This week, this colorful squares start to appear at my screen (until now only when I'm watching things on Netflix). One time the screen after a time turned into grey also, in the rest of the times the squares appear and the pc continues running "normally".

Photo of the problem:
http://imageshack.com/a/img924/8061/z33HpE.jpg


I have only played Left 4 Dead 2 after this problem appears, and it did not showed up while I was playing, I will test if the problem occur in games with games that requires more hardware.

Someone have any idea of what it can be?

My specs:
Motherboard: Asus Sabertooth Z97 Mark 2
CPU: Intel i7 4790k 4.0 GHz (up to 4.4 GHz)
GPU: Gigabyte GTX 650 TI Boost Windforce 2Gb 192-bits (actual) | Asus GTX 970 Strix 4Gb 256-bits (arriving)
Storage: 2x HDD WD 1Tb (Raid 0) | 1x HDD Seagate 3Tb (Backups)
PSU: Corsair CX750M +80 Bronze
OS: Windows 8 Pro (64-bit)

Thanks for attention and sorry if I have a poor english!

 

[Ironsounds]

Hello... Typically check the Monitor operation and cable with another computer first... But typically it means your GPU has a problem, over heating can cause this... (check your GPU fan operation, Cooler mounting, and thermal paste) or try a firmware re-flashing of the Video card as a quick fix, if temperatures are normal B /