When you move mailboxes from a Microsoft Exchange Server 2007 Mailbox server to a new mailbox database or to a new Mailbox server, such as an Exchange Server 2010 server, the move operation is not completed. Additionally, 100 percent of CPU resources are consumed on the Exchange Server 2007 Mailbox server, and the number of messages that are moved keeps increasing and can exceed the total number of messages in the mailbox.
This issue occurs because the ptagCn property of some messages is missing. This causes a corrupted index that has duplicate keys when you move mailboxes. Therefore, the move operation enters an infinite loop.
To work around this issue, you can repair the ptagCn property of the messages by running the following command at the Exchange Management Shell command prompt on the Exchange server:
Isinteg -s Server Name -fix -Test ptagcn
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about the ptagCn property, visit the following Microsoft website: