samba - Jan 2006 - Network throughput slowdown - need help

HELP!!!

Over the last few weeks, my samba throughput has slowed down big-time. I
have checked out the hardware. Network Operations has checked out the port,
no joy.

I have copied the same file over NFS and and Samba. The throughput is about
half over Samba vs. NFS. The only error messages I see are the infamous
string_to_sid messages that I have seen many questions about, and absolutely
no answers. My users are up in arms and want me to move their files to
Windows box - I really need help!

Samba Version - 3.0.21a.
Solaris Version - 8

Smb.conf file:
# Global parameters
[global]
        workgroup = TACOMA
        netbios name = GEOBASE1
        server string = TEDD Sun Server
        interfaces = 131.191.215.40/255.255.255.0
        security = ads
        realm = TACOMA.LCL
        encrypt passwords = Yes
        auth methods = sam winbind
        password server = *
        passdb expand explicit = no
        name resolve order = host wins
        deadtime = 30
        preferred master = False
        local master = No
        domain master = False
        wins server = 131.191.129.31
        winbind cache time = 36000
        create mask = 0775
        nt acl support = yes
        template shell = /bin/false
        template homedir = /export/home/geobase1/%U
        username map = /usr/local/samba/lib/users.map
        invalid users = smsadmin1
# separate domain and username with "/", like DOMAIN/username
        winbind separator = /
# use UIDs from 10000 to 25000 for domain users
        idmap uid = 10000-25000
        idmap gid = 10000-25000
# allow enumeration of winbind users and groups
        winbind enum users = yes
        winbind enum groups = yes
        winbind use default domain = yes
        printing = CUPS
        blocking locks = no
        fake oplocks = yes