Having the same problem here. Mine's not a new computer and never had the issue before about a month or two ago. Now I've noticed youtube, netflix, and at least one other stream site cause this problem to happen. Wondering if it's a driver or codec problem. Never have this issue with games or anything else.
What video card are you using? I'm running a AMD Radeon 7970.
im using the hd 7770 i dont what happend but i am having this problem less but havent got rid os this yet but its alot better than before maybe because i updated the bios