In case it would help. my crossfire setup is with two radeon HD 6870's. The old one was some stock brand that came with my PC that I ordered back in January 2012, and the new one is an XFX Black edition. I already updated my catalyst control center to the new 13.8 beta, which fixes a lot of the microstuttering issues associated with radeon crossfire.
Something else happened yesterday as well. As I was reading an article, the screen went black for a half second and came back. About five minutes later, it happened again. I'm wondering if this is connected with the garbage lines.
Anyway, as of this morning so far the lines haven't come back, as I'm watching a video on VLC.. Still a bit concerned what that was...don't want my cards to crap out while I'm playing a GPU intense game.
One other thing. I still have my old card set as my primary, and it's been through a lot of benchmarks and gaming. Maybe it's time it takes the back seat as the assistant card for the new one. Any way I can change my primary display adapter aside from getting in there and actually switching it? I checked my BIOS, it's for a MSI x58a-GD45 mobo, and doesn't seem to have an option to change the primary display adapter. Not that I can see at least.
Just noticed something else happening. The pixel-wide white borders of my windows seem to be flickering. It's hard to notice, and I thought my mind was playing tricks on me...but maybe it's worth noting.