airport extreme woes

hi all
long time reader, first time poster.
i have a 1.8ghz g5 i set up my adsl connection this week with airport extreme and a linksys router with no problems, it auto detected and asked whether i wanted to join the network.

my friend has the same mac with airport extreme and a netgear dg834(g) router and i have had no luck trying to set it up for her.
i get no signal strength at all in the menu bar icon. its as if there is no signal at all.

i know that there is a signal coming from the router because she had a rubbish d-link dwl-122 wireless usb plug in thing. it caused a kernal panic every 5 minutes so i told her to buy an airport extreme card because it would actually work. the d-link connected to the net and got nearly full signal from the router so the router is working.

i tried taking the card out and plugging it in again as id seen suggested on other threads before. but it still shows no signal. is it possible that apple sent her a dud airport extreme card? or is it possible that the signal is being lost before it gets to the aerial on the back of the g5?
should i try updating the routers firmware?
this is begining to get embarassing after i converted her to macs!!

i tried entering it manually in the "other" window, it just gives me the same "the connection could not be established message".

yeh i think im gonna have to take my airport card out, is it ok to swop the cards over often or should they not be messed around with too much?