LDAP config - Openfire 3.10, Windows Server 2008 R2

Cannot get LDAP working frm Openfire 3.10 against Windows Server 2008 R2

I am able to successfully configure Base DN and Administrator DN, and test successfully:

Base DN:     dc="mydomain",dc="com"

Administrator DN:     cn="administrator",cn="Users",dc="mydomain",dc="com"

On the next page (step 2) I am using sAMAccountName for Username field, and (objectClass=user) for User Filter. Test is failing every time and it won't find any AD admin users if I proceed to the next page, using all the defaults for group.

This is a pretty basic setup, am I missing something?

Thanks

DH