You didn't mention which OS your on, however, if it's Windows I suggest downloading LDAP ADMIN to test your connection. I found that was the best way to debug my LDAP string.
http://sourceforge.net/projects/ldapadmin/files/ldapadmin/1.6/LdapAdminExe-1.6.z ip/download
Once you're able to login and browse your LDAP, anything you need will be displayed so you can see the correct LDAP format.