samba - Aug 2010 - wbinfo -a works but wbinfo -i doesn't

We're in the process of upgrading from 3.2.14 to 3.5.4 on RHEL5.2 in an
effort to eliminate frequent complete system pauses when winbindd pulls info
from the AD2003 servers. The 3.2.14 packages were removed, 3.5.4 installed, and
the previous smb.conf file reinstated.

wbinfo -i works, as do -g -u -t -a -K and -m.
However wbinfo -i doesn't. It returns "Could not get info for
user" even though that user shows up in wbinfo -u.
The domain has been joined and kerberos checks out.

I'm looking at nss as the culprit, but nsswitch.conf is identical to all our
other working systems. Any ideas?

Oops, realized an error in my previous post. (What I meant to say is that wbinfo
works for everything except returning user info. Here's a fixed version of
my problem/question.

We're in the process of upgrading from 3.2.14 to 3.5.4 on RHEL5.2 in an
effort to eliminate frequent complete system pauses when winbindd pulls info
from the AD2003 servers. The 3.2.14 packages were removed, 3.5.4 installed, and
the previous smb.conf file reinstated.

wbinfo -g works, as do -u -t -a -K and -m.
However wbinfo -i doesn't. It returns "Could not get info for
user" even though that user shows up in wbinfo -u.
The domain has been joined and kerberos checks out.

Here's what shows up in /var/log/samba/log.winbind:
[2010/08/16 14:55:35.139832,  5]
winbindd/winbindd_getpwnam.c:138(winbindd_getpwnam_recv)
  Could not convert sid S-1-5-21-32112357098-1408373137-1283928822-1664:
NT_STATUS_NONE_MAPPED
[2010/08/16 14:55:35.139879, 10] winbindd/winbindd.c:655(wb_request_done)
  wb_request_done[26258:GETPWNAM]: NT_STATUS_NONE_MAPPED

It is interesting to note that the SID listed can be correctly converted with
wbinfo -S.

I'm looking at nss as the culprit, but nsswitch.conf is identical to all our
other working systems. Any ideas?