WRT54G WAN access failure

[Joel Roth <joelz@pobox.com>]

I'd like to ask for help setting up a used router for my
brother.

First of all, I get usual internet services without the
router:

Computer ---> DSL modem

I have problems with basic configuration: 

Computer ---> Router ---> DSL modem

The panel LEDs display normally, and 
the router gets a pingable WAN address from the DSL modem.
However....

ping google.com returns 'unknown host'

ping 74.125.45.100 (google.com) returns 'destination unreachable'

Resetting the router to factory defaults doesn't help.

Any ideas for what to try? Thanks.

Joel

-- 
Joel Roth