Error shown regarding FileMaker Pro

Hi guys,
Have you any idea regarding the error of FileMaker Pro? It says “MES SPECIAL ED 12_13.fp7” is currently in use and could not be opened. If the file is shared, you can use the Open Remote command to open the file on the network. (If you have opened the file before, check the Open Recent menu.)”.

What does it mean?
Please help.
