Damn, no luck. I installed the other NIC, and disabled the onboard one. I ran the configuration from the server console, and it acted like nothing had changed. Except that now there was no connection to the internet from the console, and no ping from other machines on my network.
Any ideas? Do I have to run any other configuration thingies?
On a side note: Plugged in the printer (Brother HL-1440, USB) and it works like a charm. A painstakingly slow-ass charm. Like file transfer, printing is insanely slow from Samba. Which is why I was trying to change the nic in the first place...