Since a couple of weeks, my iBook (G3) won't go to standby mode any more. It did previously, and I didn't change any settings. They are still set to automatic for both battery and power chord use. When I leave my iBook alone, the screen will turn off after a while, but the iBook itself doesn't switch to standby anymore, with the flashing white lamp. If I close the display, however, there are no problems, and also manually setting the iBook to sleep works perfectly. Any help?