VGA Signal Noise?

Hello everyone, I want to share a problem that I've noticed, and hope to find some answers. I purchased a used Gigabyte 550Ti OC, and it is working fine for the most part but there is one problem. I have one DVI, and one VGA monitor, the dvi hooked up directly, and the vga using a dvi to vga adapter. I've noticed, once at certian amounts of usage of my graphics card, i will get that weird effect on my vga monitor, similar to an incorrect refresh rate, its like the barely visible lines, that I only really see with a gray picture or something on the screen. I was wondering if this could be noise, considering i have an acrylic case, so there is no direct ground between the PSU and graphics card in the case, the only ground being the motherboard. Also I want to point out, if this helps, this 550Ti has a lot of coil whine. Now this may be normal, i dont know, i've had all crap graphics card up to this point, so this is my first seirous card. Any help, suggestions, and opions are appreciated.

try a different cable. thats the first thing i would sugest. also, degause your monitor.

Ill try a different cable, and its LCD, so i cant degause....

Oh and heres an example of when this happens. I have something gray open on the vga monitor, and I have minecraft sitting at the main menu, idleing, but still using ~30% of my GPU.