Gateway FPD2485W 24" widescreen LCD

Just bought one and hooked up to my Dell 4500 with 32Mb ATI Rage 128 Ultra, trying to run in native 1920X1200 widescreen mode. It appears that the card only puts out 1920X1200 at 75Hz and the monitor only takes 1920X1200 at 60 Hz, when I try the 75Hz setting I get "Frequency out of range" message from the monitor. Does this sound right, can I fix it with a new driver or ???? or do I need a new card. By the way love the monitor and the auto-rotate feature.