Strange problem with user account

[Ian A. Tegebo]

Somehow I've foobarred a user account.  It's on a system that first had
the account in /etc/passwd, but then I moved the system over to using
LDAP for user imformation.  Other accounts are fine, but this one will
not allow auth and gives the following error when trying to "su ian" as
root:

# su USER
su: setusercontext: Invalid argument

And doing the following shows

# ktrace su ian
# kdump -f ktrace.out
	...
       "<35>Feb 10 20:29:20 su: initgroups(ian,100): Invalid
       argument"
       ...
is near the end of the output.  Both "ian" and the GID "100" show up
just fine when I do:

# id ian
uid=1032(ian) gid=100(users) groups=100(users)

I suspect that something funny has happened to the account before the
migration; something like having been removed from /etc/passwd but
nowhere else.

The problem is that I can't figure out where to look now.

--
ian