Display Preference won't allow 1680 x 1050 ?
 

When I have my Hanns-G Hi221 hooked up through the DisplayLink adapter my resolution choices go from 1400 x 1050 to 1600 x 1200 (which the monitor doesn't even support)... Yet if I plug it in DVI right to the side of the computer it defaults to 1680 x 1050 no problem? What would be the issue?

Macbook Pro 17 2.33
OS 10.6.1

Thanks!

Kurt