Baffled by wireless problem

Hi all,

Baffled by this one and the dent in the wall grows by the hour.

Previously Stable SoHo wireless LAN running DLink kit.

Server/primary machine Win XP Pro, static IP etc. connected to
Hub.192.168.0.1 255.255.255.0
DLink 1000ap access point connected to hub also, config 192.168.0.206
255.255.255.0 Gateway 192.168.0.1
Comms between server and AP seem rock solid - ping response etc. over
several hours shows no varation, even when server under pressure.

2xLaptops - DLink DWL-650 PCMCIA Wireless cards. DHCP enabled. 1x Win2k 1x
Win98

Formerly - in the time it took the laptops to load, they had a connection to
the AP, DHCP took care of IP and all worked like a dream.

Came back from holiday, systems all powered off for a couple of weeks and
now when the laptop cards can get a connection - which takes much, much
longer, they cannot keep it. As soon as any load is put across the
connection when it is established it is pretty immediately dropped, without
load stable for 5mins to 3 hours.

Reinstalled config on AP - checked and double checked all settings on that
but I must be missing something pretty simple?!?

Thoughts welcome,

DavidR