I'll try to be helpful here. First thing I do is *** believe the error message *** -- sort of. It says "The file may have been moved,renamed or deleted." Well, probably not! BUT if the file/directory path cannot be seen from the MAC, we will have the same problem. Are you working under the assumption that that directory file cannot be accessed from the MAC? On the MAC, is there a way to check on accessing the file outside of APEX?
Does it have file permissions that would allow the MAC to see it?