[TYPO3] trouble in BE after installing AJAX Chat

[Harald Amelung]

Hello,

I just installed the AJAX Chat Extension (vjchat) and now cannot use the 
BE anymore. The only thing it shows is:

$item) { $res = $GLOBALS['TYPO3_DB']->exec_SELECTquery('*','fe_users', 
'uid = '.$item[1], 'username'); $row = 
$GLOBALS['TYPO3_DB']->sql_fetch_assoc($res); $items['items'][$key][0] = 
$row['username'].' ('.$row['name'].')'; } return $items; } } if 
(defined('TYPO3_MODE') && 
$TYPO3_CONF_VARS[TYPO3_MODE]['XCLASS']['ext/vjchat/pi1/class.tx_vjchat_itemsProcFunc.php']) 
{ 
include_once($TYPO3_CONF_VARS[TYPO3_MODE]['XCLASS']['ext/vjchat/pi1/class.tx_vjchat_itemsProcFunc.php']); 
} ?>

I don't know what I did wrong. Has anybody an idea what the problem 
could be?

I am using TYPO3 4.0 with TemplaVoila.

Thanks
Harald