>However when I try: 
>route add default <my gateway IP addr>
>I get:
>writing to routing socket: file exists
>add net default: gateway 18.238.0.1: File exists
>
>"route flush" doesn't help any (I get the same File exists error).

This means that there is already a default route set up (check the routing
table with netstat -r).

>Then if I try and ping a computer on the same subnet (no gateway
>inbetween) I get:
>ed2: device timeout
>
>What could be wrong now?

Unfortunately, I can't help you on this one.

--Ken