By the way, all 4 ports on the router are in use, and there is one machine that accesses it wireless.

Today, I unplugged the network printer (known to work), from the router and plugged the laptop into that port and it didnt work, but plugging the printer back in, it worked instantly.

I also tried shutting all the machines down on the network, including the router and restarting just the laptop and the router. Still nothing.

It really is as though something is upsetting the network card, but it certainly works at first.

Incidentally, once it has failed, if you right click on the '1394 Connection' and then click 'repair' it tells you that it can't complete this action because the TCP/IP is turned off, or words to this effect. This is what makes me think it's pissing the network adaptor off.