[xwiki-users] LDAP Autentication do not work anymore

Hello! Last week I was able to configure the XWiki authentication against an Windows 2008 AD. Everything worked. Now I transferred the wiki from the test system to the working environment and now the authentication do not work anymore. If I try to log in with an AD User I get the message "invalid Credentials". The strange thing is that if I use a user which has not ever entered the XWiki I get the same message. But if I log in with the admin account and look on the user list the user exists and all datas a correctly transferred from the AD, therefore the connection works but I cannot enter. What can be the reason for that, I do not understand this! Thanks, Florian