4.0.3 login hangs

[roger davis]

Our site has been experiencing a lot of problems with hanging logins on
Sun/4s running 4.0.3c. Symptoms are as follows:

1) User enters login name.
2) System responds with 'Password:' prompt.
3) User enters password, and the system hangs indefinitely.

There are no 'yp server *** not responding ...' console messages, no
nothing. This happens with root logins as well as non-root logins, and
happens with rlogins from remote machines as well as local console logins.
There are no messages of any kind in /var/adm/messages.  If the system is
rebooted, the next login attempt will usually succeed, but on several
occasions I've had to reboot machines twice before anyone could get in.

I am certain that this has nothing to do with a user's home directory (or
any other $PATH directory) being temporarily unavailable due to a down
server, because users can usually go to an identically configured diskless
machine sitting right beside the hung machine and log in with no problem
at all.

This seems to happen only with diskless clients, which in our case are
4/110s and 4/60s booting off 4/280s and a 4/380. All systems are running
4.0.3c. We are using the automounter for all NFS mounts of home directory
filesystems. I'm beginning to suspect some kind of correlation with
OpenWindows 1.0, which we've been using more frequently of late, but I've
yet to find any smoking gun.

Sun software support has been absolutely no help with this. I would
greatly appreciate hearing from anyone who has any ideas on what might be
causing this or how to run some kind of meaningful test (it's hard to see
what's going on with a machine you can't log in to). I'd even be glad to
just hear a confirmation of this problem from another site -- misery loves
company!

Thanks.