ok, on the galleries/grid_fullsize/index.php file, change line 74:
echo '<img alt="" title="' . $i . '##' . str_replace('"', '\"', $gallery['images'][$i]['title']) . '##' . str_replace('"', '\"', $gallery['images'][$i]['description']) . '" src="' . $gallery['images'][$i]['thumb']['url'] . '" width="62" height="62" />';
to:
echo '<img alt="" title="' . $i . '##' . str_replace('"', '\"', html_entity_decode($gallery['images'][$i]['title'])) . '##' . str_replace('"', '\"', html_entity_decode($gallery['images'][$i]['description'])). '" src="' . $gallery['images'][$i]['thumb']['url'] . '" width="62" height="62" />';