Strange login behaviour

We are encountering a problem on a couple of workstations. They are
logging on in an AD environment, and do successfully login and get
issued with authentication and service tickets. However, immediately
afterwards (within a second or two) the DC for the domain shows a
series of unsuccessful login attempts, firstly with bad password, then
with account locked out. We have set the number of cached logins to 0,
but the behaviour persists. We aren't sure whether the machines are
using cached, invalid credentials to access a network resource or not.
The machines are using the Novell GINA client to logon, and load an
intranet page as part of their active desktop, but so are at least 6
other machines on the same site, and none of them are having a problem.
The problem did onset at the same time that the users were forced to
change their passwords.

We're a bit stumped. Any help/advice on troubleshooting would be
greatly appreciated.

Cheers,

Mick