Svarar på min egen fråga. Det var ett känt problem, vilket tycks vara avhjälpt efter ur- och ikoppling av alla USB-sladdar.
The iMac, Power Mac G4 Cube or Power Mac G4 computer may restart instead of shutting down.
Power Mac G4 Cube
Power Mac G4
This could be caused by a USB device attached to the computer, an extension conflict, or an item in either the Startup Items or Shutdown Items folder.
Follow these steps to verify:
Disconnect all USB devices (including keyboard and mouse and any USB hubs) and power down the computer as follows:
iMac - use the front power on/off button to power down.
Power Mac Cube - hold down the power button for about 5 seconds to power down.
Power Mac G4 - remove the keyboard and connect a known good Apple Pro Mouse and shutdown the computer via the special menu.
- If the computer shuts down without restarting, it is likely the fault of one of the USB devices. Connect each USB device one by one and repeat the shutdown process until you identify which USB device is causing the fault. After identifying the suspect USB device, contact the vendor of the USB device for further instructions on resolving the issue.
-If the computer continues to restart even after disconnecting all USB devices, then it could be caused by an extension/control panel conflict, or an alias in the Startup Items or Shutdown Items folder. Remove any items in the Startup Items or Shutdown Items folder. Restart the computer and shutdown to see if this was the issue. if the computer continues to restart then make sure the issue is not caused by and extensions conflict.
See article 30929: "Mac OS: Extension Conflict Troubleshooting/Extensions Manager Features"
- If the computer continues to restart, then it could be related to the computer. In this case, start up from the Software Install CD included with your computer. Once your computer has finished starting up, shutdown the computer.
If the issue goes away, reinstall your system software. If the issue continues, reset the PRAM by holding "Command-Option-P-R" on startup. For additional information on resetting the PRAM, see article 2238: "How to Reset PRAM and NVRAM".
If you are still unable to resolve the issue, contact Apple or an Apple Authorized Service Provider for additional assistance.