SCE 2007 Management Server shows computer has not been contacted for most systems

I have installed SCE 2007 with SP1 and after 3 days the management server plus all local systems show "This computer has not been contacted yet" with an error on deployment and inventory and the Operating System is showing Windows 0.0
Laptops that are working over a VPN show the correct OS, software shows as up to date but updates are still showing unknown.
We do not use the XP firewall (we use Symantec Endpoint). I have tested RPC and fileshare connectivity by opening up eventviewer.msc from the management server to the affected workstations.
I found that the Selfupdate virtual directory was missing so I added it in manually as recommended on both the default web site (port 80) and the wsus administration site which operate on the custom port (8530 and 8531). I can connect from both the management server and from a local client. I have tried to force a reconnect using wuauclt detectnow but this makes no difference.
I also tried changing the group policy Windows Update settings (it is being applied OK) from https://managmentserver.domain.local:8531 to http://managmentserver.domain.local:8530 in case that was the issue.
I am now completely stumped as to what the problem may be. I'd like to get these basics functioning before moving on the the other errors that are now fillling up the alerts to do with performance counters.
Thanks very much in advance for any help given.