Why isn't the wireless radio in this laptop working?

Two days ago, the wireless radio in my parents T41 Thinkpad went kaput. Not that it’s completely dead, because the control panel still reads it as working properly, but it can’t recognize the signal that our router is sending (or any signals for that matter) anymore. I checked the divers, but those are all up-to-date too, so I’m stumped.

I was wondering if I could purchase an accessory wireless card to solve the problem, but would that work if the radio isn’t? Also, can anyone recommend a good wireless card.