Now that Christmas is over I'd like to address this problem again. Let's 
recap.

I have a SuSE 8.2 installation. I am attempting to use Cygwin/XFree86 to 
start an X session using XDMCP. XDMCP is not on by default so I have 
performed the following changes:

    * Enabled XDMCP in /opt/kde3/share/config/kdm/kdmrc by setting
      "Enable=true" for the [Xdmcp] section.
    * Modified /etc/X11/xdm/xdm-config to comment out
      DisplayManager.requestPort by putting a "!" in the first character.
    * Uncommented the "*" line in /etc/X11/xdm/Xaccess and
      /opt/kde3/share/config/kdm/Xaccess. Note there are two different
      lines in each file. The difference seems to be one is of the form
      of "* CHOOSER BROADCAST" and just the plain "*". I've tried all
      combinations to no avail.
    * I have only one NIC.
    * I've tried xwin -query sonslinux -from adefaria, same problem.
    * Sonslinux sits right next to me and I can login using KDE just
      fine on the console - I just can't get a remote X session from my
      XP box to put up a chooser.
    * XWin.log always seems to indicate "XDM: too many retransmissions"
      as the problem (Sample XWin.log attached). Note that XDM: too many
      retransmissions only shows up after waiting for a while.
    * Nothing listed in /var/log/messages nor /var/log/kdm.log on sonslinux.

In all cases, after making a configuration change I restart kdm.

Help!
-- 
11th commandment - Covet not thy neighbor's Pentium.