Hi Kevin, Thanks! That helped. Comparing the output of IORegistryExplorer.app of my current installation with a fresh one showed that in my current installation the entry UsbExclusiveOwner String AppleUserUSBHostHIDDevice was missing. I then tried to disable and enable Login Items & Extensions. At some point, I was successful, but unfortunately cannot say, what the culprit was. In any case, now it works. So, your suspicion was right! Thanks, Bernhard