in my test enviroment i use active directory.
Win2k8 R2 servers (domain controller and a seperate SBC machine)
clients are Win7 clients
i installed the client succesfully after a few attempts with these settings (for testing purposes):
on all machines turned of the firewalls (test enviroment, no problem, protected by corporate firewall)
on the client machine turned on FILE AND PRINTER SHARING (REALLY important, as mentioned in the release notes/(quick)manual)
Using the LOCAL administrator account (u have to activate the local admin and give it a password)
see my postings in:
Early beta released....since you have a workgroup enviroment i think there are 2 options:
1) the settings in the discovery task are not good for discovering the machines in workgroup, even itself
2) firewalls...