On http://www.atlassian.com/software/jira/docs/latest/enterprise_to_pro.html

Line that says:
Also ensure that in the permission schemes and notification schemes, only 'groups' or 'project roles' are specified (i.e., no 'Current Reporter', 'Single User', 'Project Lead' or 'Current Assignee').

Should say something similar to:

Also ensure that in the permission schemes only 'groups' or 'project roles' are specified and notification schemes don't use 'Component Lead'.