the 1394 net adapter is actually for your firewire port and NOT for a network port
Correction, it is possible
to use IEEE 1394 for IPv4 networking, though it's not normal practice. RFC 2734
gives the outline for such an implementation.
As for answering the OP, to fix this you just need to download/install the correct driver for your ethernet controller. What's the manufacturer/model of your motherboard? Or rather, what's the model of your computer?
Get back to me with that info and I'll provide a link to the driver.