Cannot join RHEL5 server to Windows 2003 SP2 Domain

Using the steps as per the RHEL-AD document (http://blog.scottlowe.org/2007/01/15/linux-ad-integration-version-4/), but I am unable to join a RHEL5 server to the Windows domain. This server does NOT use Winbind, so don't even offer that configuration as we have gotten the RHEl-AD documented steps to work in other server environments fine.

Samba Version: 3.0.33-3.39.el5_8  (and no this cannot be upgraded)

When I use the 'testjoin' command, it shows the information given is fine:

[root@sanbweb1 ~]# net ads testjoin
Join is OK

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But when I attempt to actually join the server to the domain, it errors out:

[root@sanbweb1 ~]# net ads join -U mworsham@GPOTEST.LOCAL
mworsham@GPOTEST.LOCAL's password:
Using short domain name -- GPOTEST
Could not connect to server Proj-DC.GPOTEST.LOCAL
The username or password was not correct.
[2013/01/03 12:57:04, 0, effective(0, 0), real(0, 0)] utils/net_rpc_join.c:net_rpc_join_ok(81)
  net_rpc_join_ok: failed to get schannel session key from server Proj-DC.GPOTEST.LOCAL for domain GPOTEST. Error was NT_STATUS_ACCESS_DENIED
Failed to verify membership in domain!
Failed to join domain: Success

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