Problem deleting file

Hi

I am trying to delete a file from Share Point. I previously deleted files from the same folder, but this particular file will not delete and will not allow me to 'check out'. I can however open the file and save it elsewhere without a problem. 

When I try to delete this appears:

Then when you click troubleshoot:

 When you try to 'check out'   it looks like this:

Please can someone tell me how I can delete this file? 

Thanks very much for your help,

Miriam