We recently purchased an MPU-4032 that came with the latest RELEASED firmware (1.18.0.22011). I attempted to configure it for LDAP using a document called "LDAP-DSR-AV" that's floating around on the Emerson support site, and found that when I tried to login from the OBWI, it would deny me once or twice, then hang at the login screen. Because I was sitting next to the KVM itself I was able to see that when it hung at the login prompt it was actually rebooting every time I tried to login via LDAP. It didn't matter if it was configured for "Basic", "User", or "Group" LDAP use.
It was fixed by upgrading the firmware; there's an unreleased version that the support tech sent me. As soon as I applied it, I tried to login via LDAP without changing ANY of my preexisting settings, and it worked. The tech acknowledged that the version that came with the MPU had known LDAP issues.