it make's no sense for me, to write a long description, if nobody read it...
Download_Gallery_3_ 0_0dev11 or Download_Gallery_3_ 0_0dev12 use the function Reorder() in save_files.php Ln 202 to write a new Group-Order in the download_gallery files table.
but this new function needs the new version of framework/class.order.php
take a look into this file to the first definition
older version in class.order.php ~Ln 31 - 35
private $_Table = '';
private $_FieldOrder = '';
private $_FieldId = '';
private $_FieldGroup = '';
private $_DB = null;
version from the latest core fix ~Ln 30 - 34
protected $_Table = '';
protected $_FieldOrder = '';
protected $_FieldId = '';
protected $_FieldGroup = '';
protected $_DB = null;
the different: as "private" defined Values like $_DB, $_FileId etc are only usable inside of the class, where it's defined. that means in this special case: only inside of the class order, but not in a extended function like Reorder() from the Outside like DownLoadGallery.
It is not needed, to use older WB-Version's or older PHP-Version's - it has nothing to do with this problem.
Two possible way's
1.: deactivate this line 202 in save_file.php with these code
2.: use the class.order.php from the corefix and take a look into this file to check, that you have already the latest version