Interface flickers while dual boxing in World of Warcraft

I started dual-boxing about two days ago, and at first I was getting nasty artifacting issues. I've managed to get rid of most of the artifacting, but now I notice that very rarely I'll see one section of the interface flicker(ex. The "World Map" button on the minimap) very quickly two or so times, and then stop...
I've been monitoring temperatures and whatnot, GPU never goes above 45c, CPU never above 27c...
Updated and downgraded drivers, etc, just started this morning.. or atleast that's the first time I noticed it :)
I'm running a 512mb 8800gt. No artifacts in extensive gpu stress/artifact tests, and no artifacts in a single WoW window. I know the card is fine, just not sure what is causing this.