I have a weird problem that I can't manage to describe in one word, so I'm having trouble searching for a solution.

My monitors sometimes go black for a tenth of a second. Other times, they show the image shifted a few centimeters to the left or to the right. This happens on both of my monitors, but not necessarily at the same time.

I would say it happens about once a minute, unless under heavy load, in which case it can happen every second or so. Interestingly, heavy CPU/memory usage can also cause this, not just heavy GPU usage. This only happens when they are both at 1920x1080, not when one of them, or both, are at a lower resolution. It also happens when they are in mirrored mode instead of extended desktop mode.

My GPU is obviously not at full clock speed most of the time: this happens at 350 MHz as well as at 1200 MHz. So it doesn't seem like a matter of too little performance. I'm not seeing any traditional artefacts, even when I use MSI Kombustor, only this kind of full-screen glitches. CPU stressing software isn't reporting any issues either.

I'm thinking maybe the connection between my CPU and my PCH isn't fast enough, but I can't find anyone with the same problem to confirm that. I'd rather not invest in a discrete GPU without being certain it will fix something.

Does anyone know how to search for this, or even better, does anyone have a solution? My full specs are below. Thanks in advance!

Specs:
ASUS P8Z77-M
Intel Core i5-3570K (with Intel HD 4000 Graphics)
2x4 GB AMD Performance Edition memory
Corsair Force 3 Series Rev. B 120GB SSD
Maxtor 200GB HD
Lite-On DVD-RW
Antec 350 Watt PSU
64-bit Windows 7 Professional
2x Iiyama ProLite E2208HDS display