NTM and ESXi

How do I get NTM to map ESXi Hosts ?,

I have tried accounts that are local to the Host, and Accounts that are in the Domain,..

I've been trying <username>@<domain>     and <domain>\<username>..   nothing works when I test the credentials.   The Box that I am testing on is Esxi 5.1,

I know the accounts are good as using them with vSphere works fine.

??  any idea's?  I am at a loss

Thanks in advance

- NuX