Ultra 5 can't start KDE

["Brandon Gilliam" <bgilliam@firstpreswaco.org>]

I've recently purchased a Sun Ultra 5 and have attempted to install Debian.
I've never used Debian before (I have played around with installing and
using Fedora, Red Hat, Mandrake, Corel, and Caldera on a spare x86 before
though--and I have some experience with dpkg/dselect because of Fink on
OSX). 

I made it through the install, and everything seemed to work fine until I
attempted to start KDE via startx. My screen begins to flash and won't stop.
I can see the full KDE desktop when it flashes, but I can't do anything with
it. I have attempted to reconfigure xfree86 with dpkg-reconfigure
xserver-xfree86, but nothing I do seems to help the problem. I am using the
ATI drivers and have an old 15 inch IBM monitor (2235-00N). I looked up the
horz. and vert. freq. and configured xfree with them. I think everything is
up to date package-wise, unless I missed something in dselect.

Anybody have any ideas? I'm not completely clueless with things Linux, but
not all that advanced either, so please give detailed instructions if you
can. 

Thanks in advance.