I just had a guess, you were working on the remote machine, better you try with executing sqlcmd for that particular folder and see whether you are able to access it. if "yes", then the file is in open status, if "no" then for sure it is access/permission you had for that particular folder..

(ensure you have the admin privilege on the DB where you work, it is to enable the configuration (sp_configure) to run the sqlcmd)

regards,

Prabhu