[Plugin:NextGEN Gallery Voting] Not working on Image browser

As the FaQ of the plugin suggests I icluded the php code in my imagebrowser.php as folloed:

<div id="pic-info-options">
				<?php echo nggv_imageVoteForm($image->pid); ?>
			</div>

The problem is that In the result html I get:

<div class="nggv-error" style="display:none; border:1px solid red; background:#fcc; padding:10px;"></div>

the problem seems to be in the ngg-voting.php around line: 1326
that if seems to fail for me:

if($_GET['ajaxify'] && $_GET['ngg-pid'] == $pid)

Anyone got an idea why?