With my two 5870s I have a weird problem in crossfire. I have two screens a 24''' LCD and a 37'' LED TV.
When in crossfire if I play video on the second screen it gets some odd artifacts of black(ish) horizontal lines across the bottom half of the screen (not seen a problem like it before). The problem will occur with flash content and VLC, so I think its hardware driver related.
Only solution I've found is to not have the cards in crossfire and plug the TV/Screen into different cards for watching stuff. My drivers are only a few weeks old now.
Annoying, any thoughts?