prvCreateWorkflowSession permission

Hi,

Does anyone know where the prvCreateWorkflowSession permission is located? I basically have a standard user who I have given permissions to add security roles to other users. However the insufficient users message displays on screen and when I download the log file, it tells me that the failure is:

'VerifyCallerPrivileges failed. User: PrivilegeName: prvCreateWorkflowSession...'

Thanks

Spaz