I have repeatedly tried to update Mac OS X to 10.4.6 (from 10.4.4.) on my wife's old iBook (G3, 500 MHz, 640MB RAM) using Software Update, but Software Update crashes every time before it even finishes "scanning for new updates". The OS does not seem affected and I can continue working as normal with the un-updated machine. My internet connection is fine and of course I tried repairing permissions, using MacJanitor etc etc. Are the older iBooks no longer fit for the new versions of Tiger? I have so far never had difficulties with that.