Installing UVNC: "Access Denied" & "Unable to connect to Server"

Hi - I'm a System Administrator at a College in Australia. I've just purchased & installed the full version of VENM (2008.7.8) on my desktop PC. The network I manage is a single domain network, currently using 3 subnets - 10.0.6.*/10.0.7.*/10.0.8.*. I have full administrative access to the network under my own user account, and also via the domain admin user account.

I tried pushing out Ultra VNC to a test desktop machine here in my office. I made sure the WinXP firewall was off, and file & print sharing was enabled, etc. Just in case there was anything I missed, I ran your "Simple Windows Desktop" package that configures the machine to allow VNC deployment. I then pushed out Ultra VNC to the target PC. The fastpush log shows "Checking Share access on 10.x.x.x then comes up with "Access is Denied" three times, followed by - *** Script could not find where NT is installed on the remote machine. Try using the machine's IP address rather than it's name for the target***. I've tried using the "Use IP instead of DNS option", but the same issue occurs.

I've also tried connecting to the C$ & D$ shares on this machine via the "Windows Shares" option within VENM, and this works OK!?

The target client was is the only machine in the "Default" Managed Group so far.
I've configured the following setting for the "root" of this group, within the "Group properties>VNC Settings" tab:

Use IP address instead of host name = YES

Windows/Domain Authentication = YES
(Entered Domain Admin username & p/w)

The other strange thing is that when I re-scan the PC, it now shows VNC=True - but I can't VNC to it, it just comes up with "Failed to connect to server !"