In looking at the troubleshooting section of the Portal 6 infocenter, I ran across a good troubleshooting article.
http://www-1.ibm.com/support/docview.wss?rs=688&context=SSHRKX&q1=enable-security-wmmur-ldap&uid=swg27008792&loc=en_US&cs=utf-8&lang=en
To reiterate one of the key points in the LDAP setup, you MUST disable global security before running the enable-security task.
"wpsconfig disable-security"
Then validate your LDAP setup with
"wpsconfig validate-ldap-wmmur" (the wmmur is for realm support)
Once validated, run the enable task:
wpsconfig enable-security-wmmur-ldapLabels: java, Portal, WebSphere