We've got FM 4.4 with unlimited licesnses.
Have you selected one of the fabrics when you are trying to turn performance monitoring on? PM is on a per fabric basis.
You access the performance monitor feature via a the right click menu on the fabric node in the tree. There will be options to turn PM on or off and generate reports/graphs.
Get quick and easy access to valuable resource designed to help you manage your Brocade Network.