6600go 出 external mon resolution 問題

Notebook = Toshiba Qosmio G20
Graphics = 6600go
External Monitor = LG 22" (1920x1080)
Cable = D-sub - D-sub


係 display properties 點都 set 唔到 1920x1080 resolution.

只可以 max 1440x900 (和本身notebook panel 一樣). HELP


thanks