3Com Gigabit LAN not seeing Router or Net

[Tim Rutherford]

This is a recurring problem for me - 
Asus P4P800 has builtin 3Com Gigabit LAN  (aka sk98lin or 3c940)
on my system it's connected to Linksys router & telco ADSL. Works just
fine under That Other OS (and Mandrake) but ubuntu, well..

No autoconfigure with DHCP (do I need special settings on router, BEFSR41?)
When I set IP addresses manually I still cannot "see" the IP address
of the router. Ping gives "Network is unreachable".

If I take Computer > System Configuration > Networking then I see eth0
is there, but will not Activate. The check mark stays for <1 sec. I
have manually entered my hostname (probably no benefit there) and DNS
values from my router.  Hosts has six entries, most with ip6 in the
Alias.

What's up wizards?

TIA
Tim

-- 
Please - use my NEW e-mail address:
  tim.rutherford at NCF.ca