Make sure the firmware is up-to-date too! OS X might act funny too with an older firmware. You need OS 9.1 to 9.2.1. to install the update (if needed).

Panther works great on these older G3s. If your network is WPA (not WPA2), WEP or has no password, it will wirelessly surf with the original AirPort Card. Although to use WPA an AirPort update has to be installed, which can be VERY hard to find.