some other problem i noticed: i think the whole ajax system (showing list of possible accounts while typing etc.) has a problem if you have your PHP configuration (php.ini) on
error_reporting = E_ALL (shows all PHP errors and notices). the ajax response will then contains notices about undefined variables at the beginning, for example:
<b>Notice</b>: Undefined variable: result in <b>C:\DATA\PHP_Eclipse_Workspace\P503_ZOFINGIA_WEBSITE
\htdocs\cms\code\SecurityAdmin.php</b> on line <b>99</b><br />
on my system this prevented the popup list with the possible accounts from showing...
as soon as i change the php.ini file to "error_reporting = E_ALL & ~E_NOTICE" and restart apache it starts to work again.