Can't enter IP address in TCP/IP properties

A user at my workplace has a win98 pc which is working
fine on our win2000server domain. It has a manually
assigned ip address.

I now need to change the tcp/ip properties in order to
point to our gateway to give him internet access.
The problem is that all the ip address fields (for host
address, dns, gateway...the lot) are blank - and I don't
mean greyed-out.

If I try and type anything into them, nothing appears. At
first I thought there might be some weird display problem
and that the numbers were appearing in a white font, but
if I try and type a number in (for example, to add a dns
server)and hit ADD, it shows the new entry as being 0.0.0.0

Has anyone witnessed anything like this before?

All I can think to try is to remove the tcp/ip protocol
and reinstall it, but if this doesn't fix it then he'll be
stuck with a pc that can't connect to our network. I'd
then be left doing a full reinstall of windows and all the
apps......uuuggggghhh.

TIA

John H.