Ok, so according to the User manual Specifications section. The Horizonal & Vertical settings should be...
HorizSync 31.0 - 80.0
VertRefresh 56.0 - 76.0
And in relation to the aspect ratio, the monitor defaults to 1:1. So you will possibly get some horizontal or Vertical cut off. (IE not a FULL screen display).
Also have you tried the 1920x1080 mode??
And are you using the DVI connector??