If you are using order maintenance or service job maintenance you will sometime see and error message at the bottom of the screen saying "Order in use" - this is because the last maintenance session did not complete correctly (for example if the connection dropped during the maintenance session).

To fix this go to the PAC menu, take option 4 for "Order Addendums" and then take Option 8 for "Reset Order in Use".

See attached pictures for screen shots.