Connection Speed Drop: DLINK DI-524 & Intel 2200BG

AP : DLINK DI-524 Rev A with Latest Firmware version 1.2.1

LAPTOP A: DELL D600 with a DLINK DWL-650+ 802.11G 54M Network Card (in PCMCIA Slot)
LAPTOP B: HP NC6230 with a Intel 2200BG Network Card Integrated

WEP 128 bit .

Problem:
At the same location (about 15 feet away from AP) , The D600 works prefect at 54M's speed . While the NC6230 's connection speed is very unstable. First it conencted at 54M succesfully , Then the speed start to drop to 12M quickly . I try to ping the AP to see how many packet were lost , First several minutes it works prefect but with the speed drop , more and more packet were lost . Finally I can't conect to the AP . I have to disable/enable the 2200BG again to get it work for another 3 minutes ....
During the entire period my D600 works prefect .

Another test I have done is disable the 2200BG in the BIOS and plug the DWL 650+ into the slot , the network works fine.
Looks like the Intel 2200BG does not like the DLINK stuff ...

Does anybody have similiar experience ? How can I get it out ?

Thanks!