Does your card have 2 DVI ports? I have the 6950 and on my card I have 2 mini Display ports HDMI and DVI on the first row and another DVI just below the first. To run 3 or more displays I can't use the bottom DVI and the HDMI as they are shared. If the layout on your card is the same make sure you use the DVI port on the top row.
Yes my card does have two DVI ports. Based on your suggestion, I swithced the DVI port to the top (as my DVI was connected next to the hdmi on the bottom). It still did not help, even though I thought it would work. Thank you for the suggestion.