Error / Social Bookmarks

Fatal error: PHP notice in file  /var/www/web43/html/lib/system/event/listener/DefaultAdListener.class.php  (61): Trying to get property of non-object
     Information:
  error message: PHP notice in file  /var/www/web43/html/lib/system/event/listener/DefaultAdListener.class.php  (61): Trying to get property of non-object
 error code: 0
 file: /var/www/web43/html/wcf/lib/system/WCF.class.php (281)
 php version: 5.2.6-1+lenny10
 wcf version: 1.1.6 pl 3 (Tempest)
 date: Thu, 19 May 2011 12:56:57 +0000
 request: /index.php?form=UserCarInfo
 referer: http://xxx.at/index.php?form=UserProfileEdit
   Stacktrace:
 #0 /var/www/web43/html/lib/system/event/listener/DefaultAdListener.class.php(61): WCF::handleError(8, 'Trying to get p...', '/var/www/web43/...', 61, Array) #1 /var/www/web43/html/wcf/lib/system/event/EventHandler.class.php(131): DefaultAdListener->execute(Object(UserCarInfoForm), 'UserCarInfoForm', 'readData') #2 /var/www/web43/html/wcf/lib/system/event/EventHandler.class.php(156): EventHandler::executeInheritedActions(Object(UserCarInfoForm), 'readData', 'UserCarInfoForm', 'readData@UserCa...') #3 /var/www/web43/html/wcf/lib/page/AbstractPage.class.php(65): EventHandler::fireAction(Object(UserCarInfoForm), 'readData') #4 /var/www/web43/html/wcf/lib/form/AbstractForm.class.php(93): AbstractPage->readData() #5 /var/www/web43/html/wcf/lib/form/UserCarInfoForm.class.php(81): AbstractForm->readData() #6 /var/www/web43/html/wcf/lib/page/AbstractPage.class.php(90): UserCarInfoForm->readData() #7 /var/www/web43/html/wcf/lib/form/UserCarInfoForm.class.php(133): AbstractPage->show() #8 /var/www/web43/html/wcf/lib/page/AbstractPage.class.php(46): UserCarInfoForm->show() #9 /var/www/web43/html/wcf/lib/util/RequestHandler.class.php(64): AbstractPage->__construct() #10 /var/www/web43/html/wcf/lib/util/RequestHandler.class.php(95): RequestHandler->__construct('UserCarInfo', Array, 'form') #11 /var/www/web43/html/index.php(8): RequestHandler::handle(Array) #12 {main}