Airport Card Update 2004-08-31
Now available via Software Update:
AirPort Card Update 2004-08-31 improves reliability in mixed 802.11b and 802.11g environments and is recommended for all customers with AirPort-capable computers running AirPort 3.4 and later, including AirPort 4.0.
After this update, the AirPort Driver and AirPort Extreme Driver will each be upgraded to version 3.4.3.
Apparently there is a Windows version of this update as well available via Windows Update.