your post and .txt file should reside in this directory
Paths for all mastercam components is defined in the system configuration file ( alt-F8 )
( I think under the "Files" tab ) ( the config file can also be edited in a text editor, but you have to reload the file for changes to come into effect )
Are you sure it is the post not having the correct path ( it may be the edtior path that is not found ) ???