Archive Manager for GroupWise has been installed and the nominated NDS Server also runs GroupWise. When you access the Archive Manager login page and select an NDS Tree to log into, the context drop down is blank. This also applies to E-Directory.
This is because GroupWise and NDS / E-Directory both listen on the same port for LDAP.
The following article from Novell explains that the NDS / E-Directory LDAP Port needs to be changed: http://www.novell.com/coolsolutions/qna/7127.html