Over the past fortnight I have been buying and returning GTX560ti to and from the store with the same issue. I get ripples on the screen when gaming, it can be subtle or it can be quite bad. I've done all the troubleshooting myself this weekend (I'm fairly certain it's impossible to have 3 in a row with the same issue) and I've narrowed it down to none other than the dvi-to-vga adapter which came with the card. I have obviously got it attached correctly, I've unattached it and tightened it as much as I can. I've checked for any dust or obstructions. I've replaced the VGA cable. I've tried with different monitors, they all have the same issue when using the adapter but my TV and the family 44" were fine on HDMI. I tried my monitor with my old 5770 and it worked fine, 5770 as a built-in VGA port.
This seems very strange to me - they obviously wouldn't supply the adapter if they didn't work fine 99.9% of the time. What could actually be going on here? A HDMI monitor isn't affordable right now so I'll probably have to just deal with it for a while but it would be great if someone here could maybe give a pointer.