I've been having this issue for a few months now, and it seems to be getting worse.
My monitor will suddenly go black and my audio will begin to skip/loop for maybe 5-7 seconds, and then carry on normally (but my monitor will still be black with a "no input" message on the screen). I can still type, hear audio, etc. so it seems to be purely a video problem.
My first thought was that the graphics card was becoming unseated, so I took it out and reseated firmly, tightened all screws, etc. No dice; the problem continued. Next I took out the card and disassembled it so that I could properly remove all dust with a compressed air canister. I also removed the old thermal paste under the heat sink and applied a fresh coating. This, too, was to no avail.
The problem used to only occur while gaming so I assumed the graphics processor was being overloaded/overheated, but it's gotten to the point where it will sometimes happen immediately upon system start, so I'm not so sure anymore that it's not a PSU issue or something related to voltage etc. As a result, I'm unclear on my next steps.
Computer specs below (built myself in Dec 2014); attached is a screenshot from HWMonitor. Bear in mind that the HWMonitor screenshot was taken with only my browser running (no games). While playing games I have seen the video card temp exceed 80°C. Can post more shots if needed or any other specs that would be helpful in diagnosis. Would appreciate any thoughts/suggestions - thanks in advance.