The combination Seblod and CW Multicats runs on Joomla 2.5.X verry well, but it doesen't work out of the box on Joomla 3.X (SQL-Error 1064). To make it work, you have to hack joomla_article.php, located at /plugins/cck_storage_location/joomla_article/

You have to search for
if ( $join ) { // todo:join

after that add
$catid = explode(',',$table->catid);

and the next line
$join = JCckDatabase::loadObject( 'SELECT a.title, a.alias FROM #__categories AS a WHERE a.id = '.$table->catid ); //@

have to be updated to
$join = JCckDatabase::loadObject( 'SELECT a.title, a.alias FROM #__categories AS a WHERE a.id = '.$catid[0] ); //@