hi, I have an ibook g4, (released mid 2005, Tiger). I had my computer powered up, shut the lid. An hour or 2 later, I opened it, and it was unresponsive and the screen was black. I pressed the power button for a few seconds and it booted up to the log-in screen. I walked away before logging in. When I returned, the computer was turned off, unresponsive. I tried to start it up again by pressing the power button and the ibook did not respond. No sounds made. I tried to reset the battery by taking it out, putting back in, then pressed the bottom of the case. Then, i reset the PMU, according to http://support.apple.com/kb/HT1431?viewlocale=en_US (which was done by: 1. If the computer is on, turn it off. 2. Reset the power manager by simultaneously pressing and then releasing Shift-Control-Option-Power on the keyboard. 3. Wait 5 seconds. 4. Press the Power button to restart the iBook computer. ) This was no success either, iBook still has the same symptoms. In April, I had a very similar problem (computer would not respond or boot up). After calling up the Applecare support, my logic board was replaced under my iBook's Applecare warranty. The Applecare warranty expired in August, so I presume the replaced logic board is also no longer covered (the applecare terms and conditions is a bit vague, 2.d states the replacement parts just assumes the remaining coverage of the plan). What steps should I take next ? Thank you.