I have 2 XFX HD6870 cards in crossfire in my system but when I try to connect three monitors only two if them work. I am using the DVI ports, two on one card and one on the second. I can run two no problem and can swap the third with one of the two and the monitor itself works fine so I know the monitor itself is working just cant run 3 from the dvi. Is there a solution for this problem?