Networking :: Switching Network Interface

Wondering how to get Firefox to switch to a different interface card.

Here's the scenario:
Booted with no network cable so the wifi card was initially used. (on ath0)
I then used Firefox on the web.
Later I connected in the cable and did:
ifconfig eth0 up
pump -i eth0
ifconfig ath0 down

Checked with ifconfig and only eth0 (an lo) was present.
Tried to ping my gateway with positive result.

But when I brought up Firefox again I got a "connection refused" error.
Ended up having to reboot.

Is there another command I have to issue to get Firefox to start using the eth0 card at this point?

original here.