I recently bought an Apple Wireless Keyboard and Magic Mouse for use with my G5 PowerMac running 10.5.8. Initially I tried using a generic USB bluetooth adapter, but was unsuccessful. I followed the instructions given here http://discussions.apple.com/thread.jspa?threadID=2265096&tstart=0&messageID=10943132 but I was unable to get it working. After a bit of poking around I discovered the only adapter guaranteed to work with Leopard was the D-Link DBT-120, which I have since bought. However when first plugging it in, I got a 'system extension cannot be used' error relating to the edited .kext file (see above link). Fair enough, I thought, so I tried removing all added code, to no avail. Verifying and repairing permissions has had no effect. My last straw was to try and entirely replace the .kext file from the Leopard install DVD using Pacifist, but this still has no effect. The error message is gone, but the dongle just isn't recognised by OSX. In the system profiler, it appears as a generic 'Bluetooth HCI' device under 'USB', not under 'Bluetooth', where there is nothing listed. Any ideas EDIT: the error message is now back with a vengeance... 'System extension cannot be read: The system extension "/System/Library/Extensions/IOBluetoothFamily.kext/Contents/Plugins/AppleUSBBluetoothHCIController.kext" was installed improperly and cannot be used. Please try reinstalling it, or contact the product's vendor for an update.'