Issue setting KDE resolution - Fedora 12, ATI, Dell Inspiron 8600

[Lets Go Canes]

Hi all.

Installed Fedora 12 on a Dell Inspiron 8600 laptop, dual-boot with Windows
XP.  I want to use a different resolution than what KDE comes up with by
default (default is ~1900x~1200, I want 1280x800).  However, the KDE tool
for changing resolution doesn't appear to do anything.  I googled around,
and found suggestions for using xrandr; that attempts to change the
resolution, but the only working, usable resolution with this method
appears to be the default.  The desired resolution works under Windows XP.

Any suggestions?