ADMT displays the following error message when try to migrate a user account:
ERR2:7422 Failed to move source object 'CN=XXXX'. hr=0x8007208c The operation cannot be performed because child objects exist. This operation can only be performed on a leaf object.
Some application may add configuration details to a user object. Exchange ActiveSync is an example. If you have ActiveSync, make sure the ExchangeActiveSync child object has the proper value. Or if the application is not using this configuration, you can remove the attribute value. You can use ADSI Edit to verify this value (ADSIEdit –> Default Naming Context –> Properties of the User).
If the issue is only happening on a few user accounts, you can dump the user account properties using DSQUERY command and compare them with a “good” user account value.
Other Related Blogs & Articles:
Active Directory Migration Using ADMT - http://www.sivarajan.com/admt.html
Computer Migration - Things to Consider - http://www.sivarajan.com/cm.html
User Account Migration and Merging Using ADMT - http://www.sivarajan.com/
ADMT Include File - http://portal.sivarajan.com/2011/06/admt-include-file.html
User Migration and Input File Format - http://portal.sivarajan.com/2010/12/user-migration-and-input-file-format.html