The D4J transmenu and PUArcade both use the same name for a variable: gid.  In PUArcade, this represents the id of a game.  This is explained on the D4J site here: http://designforjoomla.com/forum/index.php?topic=724.msg2360

To work around this problem, follow these steps:

1.  Open /modules/mod_d4j_transmenu.php

2.  At the beginning of the file, find this :
<?php
/** ensure this file is being included by a parent file */
defined( '_VALID_MOS' ) or die( 'Direct Access to this location is not allowed.' );
global $mosConfig_offset, $mosConfig_live_site, $gid;
// Module Params

3.  After that, insert the following code:
if (!isset($gid)) $gid=2;

4.  At the end, it should look like this:
<?php
/** ensure this file is being included by a parent file */
defined( '_VALID_MOS' ) or die( 'Direct Access to this location is not allowed.' );
global $mosConfig_offset, $mosConfig_live_site, $gid;
if (!isset($gid)) $gid=2;
// Module Params