Many characters that are allowed in folder and file names on Apple OSX or other workstations OSs are disallowed by Windows. Typically this error is an indication that you are attempting to use a file or folder path that is valid in FolderGrid but invalid on Windows.  To correct the issue, simply rename the offending file or folder using the FolderGrid WebApp.


Note: Be certain to check for trailing whitespace (a space character as the last character in the name) as this can be hard to spot but will certainly cause the "directory is invalid" error.