http://www.motherboardpoint.com/radeon-9000-pro-widescreen-lcd-t75877.htmli dont have a radeon 9000 so i cant help u but i have no problem getting widescreen res with my 8500, my geforce4mx and my geforce2mx .. but.. i connect them via VGA and like i said i know theres more limitations with dvi supported resolutions wise
checking the manual i found these supported resolutions for the 9000 pro:
Display
Resolution
Maximum
Refresh Hz
640 x 480 200
720 x 480 200
800 x 600 200
832 x 624 75
1024 x 768 200
1152 x 864 200
1152 x 870 75
1280 x 960 200
1280 x 1024 150
1600 x 900 150
1600 x 1024 150
1600 x 1200 120
1792 x 1344 75
1856 x 1392 75
1920 x 1080 120
1920 x 1200 100
1920 x 1440 90
2048 x 1152 100
2048 x 1280 100
2048 x 1536 85
and then it says a seperate resolution table for "Digital flat panel"
TMDS
Frequency
Resolution Freq Hz
165MHz 1920 x 1200 60
140MHz 1600 x 1200 60
140MHz 1600 x 1024 60
125Mhz 1280 x 1024 60
but then at the bottom it says:
The RADEON 9000 PRO MAC EDITION has been used
successfully, without modification, set as high as 3840 x 2400
resolution at 15Hz on Digital Flat Panels that support this
resolution
"VGA Monitors are supported using a DVI-I-to-VGA video
adapter."
i would try using the dvi->vga adapter and see if it makes a difference