Need help with KDE/KDM

[Rich Johnson <rjohnson@dogstar-interactive.com>]

I can't log on through kdm_greet.   All I see is a momentary  loss of 
video signal then the login screen comes back.

Has anyone else seen this?  Where should I look for diagnostic info?

Some other, possibly relevant informaion is:

The system is a brand new, from scratch stable/woody installation.

syslog, kdm.log, and XFree86.0.log don't show any errors indicating the 
failure.

/var/log/auth.log shows:
   Jun 23 10:03:35 darkstar PAM_unix[5999]: (kdm) session opened for 
user rich by (uid=0)
   Jun 23 10:03:35 darkstar PAM_unix[5999]: (kdm) session closed for 
user rich

startx from the command line will yield an X session.