Why doesn't my iBook G4 recognize my Airport extreme card?

I have three Apple products with the same Airport Extreme cards installed in them.

The machines are a 1.5 GHz Mac Mini G4, a 1.67 GHz PowerBook G4, and a 1.33GHz iBook g4.

The Airport Cards are all as follows:

AirPort Card Information:

Wireless Card Type: AirPort Extreme (0x14E4, 0x4318)

Wireless Card Locale: USA

Wireless Card Firmware Version: Broadcom BCM43xx 1.0 (4.170.25.8)

Current Wireless Network: wireless

Wireless Channel: 6

All computers easily access a Netgear router except the iBook.

It does not recognize the Airport card that is installed.

Has anyone encountered this problem, and is there a solution?

Incidentally, all computers connect via channel 11 except the iBook which indicates channel 6 as shown above.

Thanks in advance,

Craig