FYI, this has been fixed in the upcoming 2.0 release. No matter what capitalisation you use, the LDAP plugin will work fine.
I don't know if the fixes will be backported to 1.9 though (right now the developer effort is concentrated on releasing 2.0, and the changes in the plugin are somewhat tied to the new 2.0 core code).
Saludos. Iñaki.