You have a DFC mismatch between the PFC and DFC cards ie.
On the sup720 you have a PFC3B
On the 6724 you have a DFC3A.
The module will stay powered down until you reset the switch. Be aware though that the PFC3B will run as a PFC3A once the switch is reset. It is recommended to run the same version PFC/DFC cards.
Please see this link for more details.
http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/hardware/Config_Notes/78_15893.html#wp20149
Jon
