I too had the Gateway FPD2185, but returned it for another monitor after having a few late nights trying just about everything....
I will go back and get it if someone can tell me if the following corrects the problem:
I am pretty sure that the problem is somewhere with Gateway's EDID or ATI ability to read it.
Having said that, I have an ATI AIW x800XT with all of the latest drivers & software (5.13 I think).
I have just noticed that the ATI Catalyst Control Center has an option under the "Digital Panel Properties / HDTV Support"....
"Add 1080i standard format to the Displays manager"
Gateway's FPD2185W supports the 1080i or the 720p (not the 1080p).
Can someone try one of these settings with the DVI-D connection and let me know if it works? Also wondering if this would work using the Component Y Pb Pr connections.
In the short time frame that I had this monitor working, I realized that it's display is second to none & I want it back after seeing what other monitors look like.