My iBook G4 has been acting strange for the last week or so. Safari and other applications are requiring a force quit fairly frequently and today it rebooted into Darwin (just after installing the iTunes/QT and some security updates) and later it has cut out completely (battery at 95% charge). It wouldn't repond to anything (inc power button), but having left it to cool it is now working again. The hard drive has been quite 'clicky' recently too, and everything seems slower (either that or I'm getting too used to my C2D iMac!) than it used to be. The specs are: iBook G4 800MHz, 640MB RAM (upgraded from 256MB), 30GB HDD, only other upgrade was the addition of an Airport Extreme card some time ago. Any clues on what might be going wrong?