Wireless net properties not saving

Not sure this is the right forum,, maybe it should be in hardware, or
configuration, or device drivers, ......

I've got a customer who has a Linksys "G" Access point and Linksys PCMCIA
"G" adapter. It works fine but when trying to enable WEP on the card I
have to choose "Use Windows to configure my wireless network settings" so
that I can enter the WEP key manually. (I've never seen the key generator
linysys says is supposed to be in the configuration dialog.)

I have the exact setup working on my home LAN without problems. For this
customer though we enable WEP and click ok. The wireless net is found and
all is well. Then we restart the computer and no wireless lan. Upon
further investigation we find that the "Use Windows to configure my
wireless network settings" is no longer selected. We select it and all is
well again. Reboot and again, no lan and the setting is unchecked again.
It won't save the settings.

Anyone know why this might be happening?

Windows XP Pro, SP1, Dell Lattitude C400, 512MB RAM.

J