LDAP problem

Hello there... I have a problem with LDAP and need your advice... I built a test script with help from the manual which authenticates a user and does a simple test query (cn=*). the test script works fine, no matter what protocol version it uses, on any (internal) client computer. The problem occurs when I built the same lines into my intranet-app. After connecting successfully to the server (ldap_connect) the script is unable to bind to server (ldap_bind -> cannot contact server...). LDAP works fine all the way, we are using OpenXchange... Would be great if one of you have an idea! Thanx a lot... BB