Something that I've noticed is that both the Videocards and Eternet cards like to use IRQ 15 (or is it 11) as their address.

Either you can go with the above suggestion,

or try to uninstall the videocard, turn off the computer, put in the ethernet card and install both cards and hope it results the conflict,

or (the painful suggestion) format your puter, remove all cards except the video, install ME, then the vide drivers, then enter the network card, then install it's drivers, then follow that for each card until done. (It's a last solution for IRQ conflicts)