Finally got it figured out with support...

Lothar's ECMA LDAP function was working in Dev, QA, on another server,
but not on the one server with the right replicas to run it on.

Every attempt would get a connection error.

Turns out the problem was a conflict between ldap.jar and xcd-all.jar.

If you have the User App driver on the engine, then you can have this issue.

This is supposedly fixed in the 4.0 UA driver. I will pass this on to
Lothar, since his drivers rely on it. It is a built in function as a
Package in 4.0 so should be ok in a 4.0 UA world.