BT Voyager 2100/1010: hair loss!

Trying to set up a wireless network between:

Desktop PC, running Windows XP, connected - by cable - to BT Voyager
2100 ADSL MoDem/router. This PC is connecting fine to ADSL through this
router - in fact, that's what I'm typing this through.

and:

Desktop PC, running Windows 98SE, and BT Voyager 1010 wireless USB
accessory

or:

Laptop PC, 98SE lite, no-name wireless card.

All (!) we want to do is be able to connect to the internet (e. g. web
and email in/out) from the '98 machines.

The '98 machines can "see" the Voyager, in that when we ask them to say
what they can see, the SSID (?) we've created for the Voyager2100 is
visible along with one or more others nearby. When we tell them to
connect, they _seem_ to do so, in their different ways: for example, on
the laptop, the utility window disappears when I click on connect.

BUT: a browser cannot load pages from the internet. AND: on the laptop
at least, the "link" light doesn't come on. On the same laptop, I can
connect - and download pages via! - one of the other networks it can
see (something with "belkin" in it) - obviously a neighbour has an
unsecured connection! When I do this, the link light _does_ come on. If
I then bring up the list of visible networks again and try to connect
to the Voyager one, the link light goes out.

I don't think it is the security setting, because (a) the behaviour is
the same whether I have it enabled, and with the correct keys entered
at both ends, or if I have it disabled, and (b) with it disabled, the
boxes in the connection utility on the laptop where I enter the key are
greyed out, which suggests to me that the laptop is detecting whether
encryption is required or not.

Another thing: the instruction manual, help files etc. for the 1010
(the USB thingy) talk about "passcodes" [IIRR], as something that can
be used when connecting together items from the BT Voyager range, with
"keys" being something used for connecting non-Voyager equipment;
however, the 2100 (the ADSL/Router) files etc., as well as the browser
interface to the router itself, do not seem to have any knowledge of
these pass-whatevers (so we used keys, until we decided to try with no
encryption at all and still didn't get anywhere).

Was up until getting on for four this morning trying to sort it - apart
from anything else, it's for my blind friends (I'm using his identity
to type this), and I want to try to fix it for them within the few days
I'm visiting.

Help!