Thanks for the responses! Unfortunately, screen tearing is not the issue as these wave-like patterns can be seen on the entire screen when the stress tester is in windowed mode or even minimized.
And I don't think the lack of power is an issue either because this strange glitch almost vanishes when I enable "heavy mode" in OC Scanner, which actually draws more power than when it is disabled. A high quality 560W PSU is also way more than enough to run a GTX 670.
Someone claims they fixed this issue by using another cable, and it does look like some sort of faint interference issue, but then why would it only happen under stress testing? That makes no sense! D:
EDIT: Actually, you may be right about it drawing too much power for the PSU... OC Scanner has a rendering delay option that reduces power draw. Increasing the delay slightly seems to reduce or fix the wave-flickering. But then why does increasing power draw also reduce (but not entirely fix) the flickering? @_@
I need to figure this out before the 15 day easy return/exchange period for my graphics card ends! I sure hope it's not the PSU, because RMAing that would be a pain in the butt.
Edited by Dark Fact, 25 June 2012 - 08:00 PM.