Hi,
Try changing line 106 of 'application/models/timeslot/Timeslots.class.php' from:
$postFrom .= ") LEFT OUTER JOIN `pr` AS `ws" . $i . "` ON `pr`.`p" . ($wsDepth + $i + 1) . "` = `ws" . $i . "`.`id`";
to:
$postFrom .= ") LEFT OUTER JOIN `".TABLE_PREFIX."projects` AS `ws" . $i . "` ON `pr`.`p" . ($wsDepth + $i + 1) . "` = `ws" . $i . "`.`id`";
(Changed the first `pr` for `".TABLE_PREFIX."projects`)