Can't use 1280*720 on my 27'LCD

I just upgrade my graphic card from 9800Pro to BFG 6800Ultra with Dual DVI output. Since my Syntax Olevia 27' LCD has DVI input, I tried to connnect my Dell 19'Ultra Sharp and Syntax LCD both using DVI. There comes the problem: can't set Syntax on its natural resolution to 1280*720 with DVI no matter how I tried, I even add this resolution in N-View program. It did add it, but nothing can be displayed at that resolution. When I use my 9800Pro, the VGA connection is doing very good at 1280*720. Also, I found out that the VGA adaptor that comes with 6800Ultra is doing poorly, the characters on Syntax is distorted, way worse than my 9800Pro. I did reinstall the newest 66.93 forceware, same problem. Can anyone help me how can I solve this problem? I even don't know if it was the problem of the graphic card or LCD or my setting. Thanks!