Connection to exchange server

[Tim]

I can't connect to exchange server to get mail, and I am
about out of ideas. I think I have tried everything I can
find anywhere on the web......

When I try to resolve the name, I get "This action could
not be completed. The connection to the MS Exchange server
is unavailable. OL must be online or connected to complete
this action".

I am on a wireless network behind a firewall, but the
firewall allows OL, and I have configured other machines
to connect from the same location(it makes no difference
if I take the firewall down anyway). Other machines can
access any account on the exchange server - my machine
can't access any. It can ping, and I can ping with or
without VPN (to different servers). I have rebuilt my
machine from the OS up, and upgraded to OL2003 (but the
problem started last week before I upgraded). The host was
upgraded in the meantime to OL 2003 also, but no
difference.

Apart from the usual VPN, firewall etc advice, does anyone
knnow of anything else that might prevent a single machine
from connecting to the server (or apparently even seeing
it when I try to resolve the account name)???? My exchange
hosting service is out of ideas too....