User cannot be found when creating sub-site, Document Library, etc.25 Jun 2011 | SharePoint 2010
Had an issue where the user who enabled the Publishing feature on a site had been migrated from one domain to another, and
stsadm -o migrateuser had been performed on their account without errors. After the migration, when someone attempted to create a Document Library, sub-site, etc., SharePoint would generate a “User cannot be not found” error message (although the item would be created).
It turned out that the Publishing workflows (as well as other site-wide workflows) were listed with the old account. Opening and simply resaving the workflows as a user account that had been migrated fixed the issue.