I have problem to add a new NOWS SBE 2.5 server to an existing tree.

I'm using the WEB administration interface > add-remove > eDirectory install.

At the end the message is:
"There was a problem with the component installation.
NDS Configuration failed. Please re-install and verify all IP Addresses, Server Contexts and Passwords. If the install involved a remote tree, also verify time synchronization between the servers."

Please help