Howdy guys, so for the past month and a half I've had this reoccurring issue with my computer where essentially I'll be browsing the web/watching a video and playing a game and all of a sudden my screen will lag, the sound will lag and stutter, and on occasion the computer itself will freeze up and then continue back to normal. This happens most often when I am watching a Youtube video and playing Runescape, browsing the web with a video playing, or when I launch certain games (The culprits being Saints Row The Third and Insurgency). I've updated my drivers for my graphics card and motherboard, I've done a HDD scan for errors, and I've tried rolling back drivers and nothing seems to work. Any help would be greatly appreciated.
Thanks!

Check your Scheduled Tasks in Control Panel :) There maybe a program running automatically every so often slowing your system down.

I checked the scheduled tasks and the only ones on there are for Google updates and a few cleaning utilities I have disabled by default.

Good call I like this one - also how about heat? Do you have a solid power supply and an extra fan or two? Do you have a decent GPU but the power supply isn't up to snuff?

I have 4 fans on my GPU and the computer runs at a steady 27-30C while under heavy load. If overheating is the problem then I might have a faulty heatsink or...?

Hmm maybe but if you're running 4 fans and at those temps I wouldn't jump to the heatsink yet - I was hoping you'd say I don't have a fan and my 300 W PSU is powering a 770. But you sound well cooled - I'd see if anyone else can give you a better idea before you pry off your heatsink and buy some thermopaste.

Yeah, I have an aging 6950 2Gb and it is usually never running hot. I clean my PC once every two months or so now so that should not be the problem.

Will be monitoring this thread because this has been happening to me too for the past couple of months. Exactly as you describe it, with YouTube leading as the trigger. I have been blaming the Flash player, but for no clear reason.

Can you check your resource monitor, probably there is a process with high cpu usage.
(also you can try to disable your vga hd sound driver. I solved similar problem like this)
For flash player > open settings and remove thick from hardware acceleration.

See, that is EXACTLY what I thought as well, and I tried updating it to the newest ones and the beta and that SEEMED to fix it but it didn't. Done all of that. Still no fix. :/

Try updating Flashplayer.

Did that, still persists.

Is there any procces with high cpu usage when you get lag?

Not that I have noticed. I DO however recall that my lag will result in an Internet connection loss for a moment and it goes back to normal afterwards.