I've had this a couple of times now, where large areas of the screen will flash with white lines on blocks of translucent black, quite often in the background of the scene. The game remains sort-of playable, and I know a game restart has always fixed it (though that's tempting fate isn't it? I just came off a game with it happening, I bet it'll happen next time just to really bug me!)

I did check to see my case fans are running at proper speed... I down-clocked my graphics card (7950) from 950mhz to 900mhz (memory at stock). That didn't help.
I fiddled with in-game settings too.. changing a bunch of them at once seemed to provide a temporary fix: vysnc, frame buffer, overall quality settings (toggled between low and medium), lighting SSAO/HDAO(?)... but it may have been a coincidence as it came back.

The flickering / flashing continues in the in-game menus after quitting a match.

The reason I didn't just bail out and restart the game is that I was getting good scores - so I'd love to find either the reason why it happens (I did Win+tab earlier...) and if there is a way to reset the renderer in-game. (Or restart the AMD driver)?

Short video of the problem... though this looked different from the previous match where it was happening - it's more in the foreground in this round.