I've installed the RSAT tools, and set the router option in the DHCP Scope options as mentioned in that post, still to no avail.
I've booted in safe mode with networking and still no joy.
I tried booting with a linux disk, and I have no problems.
So it must some kind of software issue, rather than incorrect settings, well I think, either that or I have a nasty infection, one that's deeper in the system, that my usual programs haven't detected.
This has happened in the past. Is there any chance this could be moved to the malware forum, and have somebody check it over, possibly for some kind of rootkit?
I've exhausted all options I can think of, and on the advice you have given me.
Regards
Dave