Mambal
Client Migration does not utilize the PST Locator task.
As Paul suggests, have a look at the Articles, in particular this one:
https://www-secure.symantec.com/connect/articles/migrating-pst-files-symantec-enterprise-vault-2007
which is still applicable to v8.
As to your error: Are you able to launch the Outlook integrated EV Search?
Are you able to archive and retrieve items?
Cheers