I seem to be going through a similar problem – I get the same "Could not connect to the LDAP server. Please check your LDAP configuration." message -- see my post at http://forum.pfsense.org/index.php/topic,38257.0.html
When I run the test, it does connect and bring up some OUs and objects for me, as described in the link, but I'm stuck at either allowing all users in the domain to log in (by manually adding CN=Users to the Authentication containers) or none, as any other group I enter doesn't seem to work.
I note that you're trying to authenticate against an SBS – while I'm using a Windows 2003 standard server, the domain itself was created on an SBS 2000 server many moons ago but has since been migrated to non-SBS DCs.
I wonder if the issue is the AD/OU structure created by SBS being slightly different than a non-SBS-created AD, which the LDAP connector in pfSense in its current form doesn't know how to traverse properly.
UPDATE: See my post linked above for a workaround for filtering by group.