I am running Cygwin-X on Windows XP, connecting to a Gentoo workstation
via xdmcp.  If I connect to a session running Gnome one processor on my
Windows machine spikes to 100% usage and stays there.  Memory use
appears to remain constant and the X-session is responsive.  The CPU
doesn't spike while GDM is active, just while the Gnome session is active.

If I use a different window manager, such as Blackbox, the CPU does not
spike.  Other activities on the XP machine seem normal and other
programs seem normal.  I have closed xdmcp session, close and restarted
Cygwin, and rebooted XP.

I ran Windows Update last Friday and shut down my Windows machine for
the weekend.  I didn't notice anything amiss before then, though I
cannot guarantee there wasn't a problem.  There were some Gnome updates
in Gentoo that I emerged recently, I think it was just at the beginning
of last week or the previous week, but I don't recall noticing the CPU
spiking afterward.

In order to try solving the problem I ran the Cygwin setup program and
let it install all new updates; when that didn't work I re-ran and
force-reinstalled everything.  The core Cygwin DLL and X libraries were
not updated - they're current according to the setup program and the
updates that were found were for some utilities (I didn't record which
ones).

I have tried googling this with terms like "cygwin xdmcp gnome cpu 100%"
and a few variations of that but I haven't found anything relevant (or
recent).

Is this a Cygwin problem?  CPU usage is normal on the remote Linux box
(the client, in X parlance), and it seems coincident with MS updates so
it seems reasonable that it's not a direct problem with Gnome per se but
with the XP machine (the server).

Attached is the output of cygcheck