When I first made up my core machine I used a load of old parts, just to see if I got on with LMCE and whether it did what I wanted it to do. Consequently I used 2 god-knows-how-old network cards that I'm unsure of the speed or model of, and everything worked and life was peachy.
Now I'm getting a bit more serious. I've upgraded my internal hub to a gigabit switch, and bought 2 new D-Link DGE-528T network cards for the core machine (as well as some other goodies, like a Nokia 770 and wifi access point). I thought that it would be a simple case of swapping the old card for the new in my core, but when I did so, nothing worked. I couldn't see the core from any machine that it was supposed to be assigning IP addresses to, the core couldn't see the NAS drive, no machine on my network could access the internet etc. I concluded that the network cards didn't work (everything was lit up correctly though) and swapped them back to the old ones, which work fine again.
The question is: what do I need to do to get my shiny new cards to play nice with LMCE? I'm sure theres some easy step that I've not thought about, but what is it!?!?!