Same problem as you describe with the 305T and the Radeon HD4850 - tried 2 manufacturers for the HD4850 and both reported a max resolution of 1280x800 and refused to go higher (except in the fake "sliding desktop" scheme). I should be getting an EVGA 640-P2-N828-BR GeForce 8800 GTS tommorrow and will see if that works.

This same monitor on the same computer system DOES work!!! with
Radeon X1900 XTX
and
ATI FireGL V3300

so I don't see why these other drivers get it wrong.

ATI responded asking me to install the monitor driver. The monitor driver is NOT needed according to the user manual, and the driver is not available for download from Samsung. If someone can provide the driver for me, I can continue with ATI to solve the problem. Is it, as they claim, on the CD (which I cannot find now)???