Wireless AP messes with IP addresses

Hi,

my NTL telephone modem (in UK) promotes an IP to the Wireless Access
point (DLink DWL 2000 AP). This is supposed to generate subnet IP
numbers, which are picked up by the clients. BUT ...

IF the AP is configured as DHCP server, then it ONLY uses the standard
IP number which previously was used to adress the AP and to comunicate
with it (some 192.168.0.* numbers). It gives such IP numbers to the
clients, although this is useless, since the AP is not any more in the
same subnet.

IF the AP is NOT configured as DHCP server, it provides some kind of
IP (e.g. 169.254.*.* or 81.?.*.*), but this again does not lead to the
consequence, that I can communicate to the outside world.

Any ideas ?

Dietrich

PS: Apart from the mentioned info ... the AP automatically gets the
IP from the Modem and the PC as well from the AP.