Error: "You cannot continue logging in at this time."

[josh hough]

For several months I have occasionally received an error when logging into
OS X.  Here it is, verbatim:

"You cannot continue logging in at this time.  There is a problem that
prevents you from logging in at this time.  Please contact your system
administrator for help."

I click OK, try again, and it works fine.  It's not consistent and it's not
a terrible inconvenience, but I wonder if it points to something more
serious.  The G4 started doing this right out of the box, almost.  I have
been through several system updates (through 10.2.5) with no change to this
behavior.  There is one admin account, one regular account, and root.  So
far only the admin account has seen this.  The machine is not on a network
and nothing unusual has been installed.  Any ideas?
-josh