ADMT v3 Error

I am setting up ADMT v3 for an Interforest Migration and am getting an
error when I try to run a test group migration.

The error is: "Err3:7585 The account replicator is unable to
continue. Access is denied."

Target forest/domain is Windows 2003 (Windows 2003 Mode)
Source forest/domain is Windows 2003 (Forest=Windows 2000 Mode and
Domain=Windows 2000 Mixed Mode).

Do I need to upgrade the source domain and forest to Windows 20003
functional level?

The account I am using has the following permissions:
Domain Admins in source domain
Administrators in target domain
Local Administrators on ADMT box (Windows 2003 member server in target
Delegated Full Control at the domain level in target domain

There is an external trust between the child domain in target and
child domain in source. Should this be a forest trust instead? There
are three child domains in source domain that I will be migrating to
one child domain in target. I would need to up the functional level
on the source forest to create a forest trust.

Here is my log file:

[Settings Section]
Task: Group Migration (17)
ADMT Console
User: SourceDomain\migrator
Computer: migration-pc. (MIGRATION-PC)
Domain: (targetdomain)
OS: Microsoft Windows Server 2003 R2 5.2 (3790)
Service Pack 2
Source Domain
Name: sourcedomain.sourceroot.local (sourcedomain)
DC: sourcedc.sourcedomain.sourceroot.local (sourcedc)
OS: Windows Server 2003 5.2 (3790) Service Pack 1
Target Domain
Name: (targetdomain)
DC: (targetdc)
OS: Windows Server 2003 5.2 (3790) Service Pack 2
Intra-Forest: No
Migrate Security Identifiers: Yes
Update Rights: No
Fix group membership: No
Conflict Option: Ignore
Migrate members: No

[Object Migration Section]
2007-07-18 09:32:33 Starting Account Replicator.
2007-07-18 09:32:34 ERR3:7585 The account replicator is unable to
continue. Access is denied.
2007-07-18 09:32:34 Operation completed.

Anyone have any ideas?