Thanks Martin, tried that and some other tweaks but nothing makes any difference. Think I'll just have to live with this one for a while although I might source a new network card to replace the onboard at some point. Just have to figure out a way to free up a slot...
I've tried swapping just about everything from the PCH to cables and 100 switch but the 1000 is built into a cabinet and I don't have a replacement anyway. I'll keep an eye open for a bargain 5 port giga-switch and see if that helps, but I'm convinced there must be a setting or driver issue on the server because it was working so perfectly on XP. As I say, I can work around it just now but you know how it is, it's one of those things that I just can't stop mulling over in the back of my mind, sad git that I am.