Quote Originally Posted by Capricorny
Just a short update: I plugged in an old Billionton PCMCIA card, ran "ifup eth1" and it worked immediately. But what to do with the built-in Realtek 8139 based interface, I still don't know...
I only have one interface in all of my PC's...
I had to add the above pump command to both PC's after a HD install.

After booting with the PCMCIA card not installed, do you get an error in the dmesg report. Also, do an lsmod with a HD boot and with a CD boot. Look and see if the drivers for you onboard LAN were loaded on the CD boot and not the HD boot.