System freeze when logging out

[Lorin Pino]

Sometimes (once every two or three days) when logging out lorin (does 
not happen when logging out from my wife's), the greeter will only come 
up part way and stop.  There will be a white screen with the outline of 
where things should be on the screen.  I am running 5.10, with the 
Debian Blue List greeter.  The only thing I can see in logs is:
localhost gdmgreeter[8703] Theme broken: must have pam-message label!

Any idea why this is an intermittent problem, and how to fix it?  
Everything works fine after a reboot, so it is only an annoyance.  Thanks
~Lorin