We have the same problem with SA-4000 6.0R4-1 (build 12783)
I found out that it is related to the authentication:
info -  - UserDomain\user(CorpRealm) - 2008/06/19 16:31:58 - Getting directory information from auth server "CORP"
info -  - UserDomain\user(CorpRealm) - 2008/06/19 16:34:29 - GetUserGroups(DC-ip, UserDomain\user, Domain, Admin, no, , yes, 2, 15, vc00000a25ca37, Computers, 0)
It takes 2.5 minutes to get the AD stuff. That is very painful!
Authentication protocoll is Kerberos NTLM V2 and NTLM V1
Used LDAP to get Realm. We tried a lot to set the REALM fixed without luck!
The User is in a different domain then the Group. I see in the log that all groups from the user domain are fetched
I appriciate any suggestions on that!