>> I think what is happening is that the (NT) DHCP servers - over which I have
>> no control - decide that a particular MAC address will have a designated IP
>> address until it's lease expires - regardless of which segment it is on.
>> 
>        Just curious - have you nuked /var/db/dhclient.leases* ?

Yep, that was one of the first things I tried - several times ..
One other thing I tried was to change the dhcp-client-identifier (from
the original which contained MAC address - by incrementing 1st digit) ..
It didn't work either - because server still seems to pick up REAL MAc address.

It occured to me last night that my original client-conf requested 'routers'
but didn't require them. This was OK a few months back when we we running
'routed' - but we have new routers here which apparently don't respond to
'routed'  requests.  So I have changed our standard setup to insist in
'routers'.  Maybe that will fix it ..

G.