In sources/admin ... open the file ManageThemes.controller.php
find this block (around line 458)
if (empty($this->_req->post->options))
$this->_options = array();
if (empty($this->_req->post->default_options))
$this->_default_options = array();
replace the above with
$this->_options = $this->_req->getPost('options', '', array());
$this->_default_options = $this->_req->getPost('default_options', '', array());