Index: typo3/sysext/cms/ext_localconf.php
===================================================================
--- typo3/sysext/cms/ext_localconf.php	(revision 7072)
+++ typo3/sysext/cms/ext_localconf.php	(working copy)
@@ -193,5 +193,7 @@
 $TYPO3_CONF_VARS['SC_OPTIONS']['t3lib/class.t3lib_tcemain.php']['processCmdmapClass'][]  = 'EXT:cms/tslib/hooks/class.tx_cms_treelistcacheupdate.php:&tx_cms_treelistCacheUpdate';
 $TYPO3_CONF_VARS['SC_OPTIONS']['t3lib/class.t3lib_tcemain.php']['moveRecordClass'][]     = 'EXT:cms/tslib/hooks/class.tx_cms_treelistcacheupdate.php:&tx_cms_treelistCacheUpdate';
 
+	// registering hook to update usergroup list for be_users
+$TYPO3_CONF_VARS['SC_OPTIONS']['t3lib/class.t3lib_tcemain.php']['processDatamapClass'][] = 'EXT:cms/tslib/hooks/class.tx_cms_updateusergroups.php:&tx_cms_updateUsergroups';
 
 ?>
Index: typo3/sysext/cms/tslib/hooks/class.tx_cms_updateusergroups.php
===================================================================
--- typo3/sysext/cms/tslib/hooks/class.tx_cms_updateusergroups.php	(revision 0)
+++ typo3/sysext/cms/tslib/hooks/class.tx_cms_updateusergroups.php	(revision 0)
@@ -0,0 +1,104 @@
+<?php
+/***************************************************************
+*  Copyright notice
+*
+*  (c) 2010 Georg Ringer (typo3@ringerge.org)
+*  All rights reserved
+*
+*  This script is part of the TYPO3 project. The TYPO3 project is
+*  free software; you can redistribute it and/or modify
+*  it under the terms of the GNU General Public License as published by
+*  the Free Software Foundation; either version 2 of the License, or
+*  (at your option) any later version.
+*
+*  The GNU General Public License can be found at
+*  http://www.gnu.org/copyleft/gpl.html.
+*  A copy is found in the textfile GPL.txt and important notices to the license
+*  from the author is found in LICENSE.txt distributed with these scripts.
+*
+*
+*  This script is distributed in the hope that it will be useful,
+*  but WITHOUT ANY WARRANTY; without even the implied warranty of
+*  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+*  GNU General Public License for more details.
+*
+*  This copyright notice MUST APPEAR in all copies of the script!
+***************************************************************/
+
+
+/**
+ * Class that hooks into TCEmain and listens for updates to users and usergroups
+ * to update the cached usergroup l8ist
+ *
+ * @author	Georg Ringer <typo@ringerge.org3>
+ * @package TYPO3
+ * @subpackage tslib
+ */
+class tx_cms_updateUsergroups {
+
+	/**
+	 * waits for TCEmain commands and looks for changed pages, if found further
+	 * changes take place to determine whether the cache needs to be updated
+	 *
+	 * @param	string	TCEmain operation status, either 'new' or 'update'
+	 * @param	string	the DB table the operation was carried out on
+	 * @param	mixed	the record's uid for update records, a string to look the record's uid up after it has been created
+	 * @param	array	array of changed fiels and their new values
+	 * @param	t3lib_TCEmain	TCEmain parent object
+	 */
+	public function processDatamap_afterDatabaseOperations($status, $table, $recordId, array $updatedFields, t3lib_TCEmain $tceMain) {
+		if ($table == 'be_users') {
+			$this->processUpdateUsers($recordId);
+		} elseif ($table == 'be_groups') {
+			$this->processUpdateUsergroups();
+		}
+	}
+
+	/**
+	 * waits for TCEmain commands and looks for deleted usergroups, if found
+	 * the usergroup list is updated
+	 *
+	 * @param	string	the TCE command
+	 * @param	string	the record's table
+	 * @param	integer	the record's uid
+	 * @param	array	the commands value, typically an array with more detailed command information
+	 * @param	t3lib_TCEmain	the TCEmain parent object
+	 */
+	public function processCmdmap_postProcess($command, $table, $recordId, $commandValue, t3lib_TCEmain $tceMain) {
+
+		if ($table == 'be_groups' && $command == 'delete') {
+			$this->processUpdateUsergroups();
+		}
+	}
+
+	/**
+	 * Update the cached usergroup list of all users
+	 *
+	 * @return	void
+	 */
+	protected function processUpdateUsergroups() {
+		$userAuthGroupObj = t3lib_div::makeInstance('t3lib_userAuthGroup');
+		$userAuthGroupObj->user_table = 'be_users';
+
+		$users = t3lib_BEfunc::getUserNames();
+		foreach($users as $user) {
+			$userAuthGroupObj->setBeUserByUid($user['uid']);
+			$userAuthGroupObj->fetchGroupData();
+		}
+	}
+
+	/**
+	 * Update the cached usergroup list of a given user
+	 *
+	 * @param	int		Id of the user
+	 * @return	void
+	 */
+	protected function processUpdateUsers($userId) {
+		$userAuthGroupObj = t3lib_div::makeInstance('t3lib_userAuthGroup');
+		$userAuthGroupObj->user_table = 'be_users';
+		$userAuthGroupObj->setBeUserByUid(intval($userId));
+		$userAuthGroupObj->fetchGroupData();
+	}
+}
+
+?>
\ No newline at end of file