Desktop not being displayed

[Eric Schwarzkopf]

I just installed YellowDog Linux 2.3 on my "Old World Mac" Power Computing
Power Center, and everything looks and ran great. I was asked to pick the
type of monitor that is attached to my Mac and the list did not include the
Power Computing 17" Multiscan model# PCC51189, so I selected one of the
generic ones listed, and finished the installation and restarted. Well YDL
starts to boot up and it gets to point where it asks (TEXT MODE only
GRAPHICAL not working) for user name and PW, and then I type "startx" to
load the GUI desktop, and all I get is a blank screen, I know that the
desktop has loaded because I can hear the startup sound, I just don't have
video.
Does anyone know what the correct setting are for a "Old World Mac - Power
Computing 17" Multiscan model# PCC51189"?
Thanks
Eric