I'll start by saying this issue is a great candidate for a support call if that's available to you. However, you can get a better idea of what's happening on your own with the following:
Orphaned locks can be caused by application crashes or critical errors during some geodatabase operations. There is also an ArcGIS server bug in 10.1 when applying simultaneous edits via feature service causing these types of geodatabase issues.
When was the last time the Sql Server service was restarted? Has it been longer than the date seen in the Administer Geodatabase dialog? If so, try bouncing the service and check the locks again.
If you can confirm that there are no users currently making valid connections you can query the SDE locks and process_information tables to get a fairly accurate view of potential orphaned connections and locks.
SELECT * FROM sde.sde_process_information;
SELECT * FROM sde.table_locks;
SELECT * FROM sde.layer_locks;
SELECT * FROM sde.object_locks;
SELECT * FROM sde.state_locks;