Change Authentication Provider on MOSS 2007
When you try to change Authentication Provider for a Web Application, you could receive this error:
An object of the type Microsoft.SharePoint.Administration.SPWebApplicationProvisioningJobDefinition named "Provisioning 8b10f967-bf6e-482c-9bde-01edec2ac953" already exists under the parent Microsoft.SharePoint.Administration.SPWebService named "". Rename your object or delete the existing object.
Probably your old action is still pending for SharePoint.
Go to Central Admin -> Operation -> Timer Job Definition -> Delete the Provision Web App