I just picked up a MSI R5770 Hawk card from the parts picking megathread. I run dual 2560x1600 monitors (LG W3000H, for what it's worth) but for some reason I can only get the native resolution for the monitors through the DVI interface. My previous card was a Sapphire card from about two years ago with dual DVI interfaces on the card, which worked without problems.
However, when using the DisplayPort interface with the dongle included in the package and an appropriate DVI-D Dual Link cable, windows and catalyst both detect the monitor's max resolution at 1280x800. The monitor is, however, being detected as an LG W3000H, if that matters.
I've downloaded updated drivers, and that doesn't seem to fix the problem. Any idea what, if anything, I've done wrong?