Thanks Plastic.
I had reinstalled practically everything...except an old version of MidiMonitor somewhere in my utilities folder. Since I had used it before without any problems (version 1.0.2) I went from a fault in the MIDI hardware setup. But maybe OS X and it's intricate system of...
I just upgraded my dual 1 gHz G4 QS to 10.2 and tried to get MIDI working via the new control app "Audio MIDI setup" (it's in Utilities). But my rather new MOTU FastLane USB MIDI interface with new driver installed does not respond anymore. It worked fine under 10.1.5. But now it's gone. Am I...