Backup and Delete the policy that you had created for Device control. Restart SEPM. Update policy.
You might need to reboot one of your SEP machine just to verify that the new policy with no Device control is implemented.
check if this works.
How to Export and Import a Symantec Endpoint Protection client policy
http://www.symantec.com/business/support/index?page=content&id=TECH190053