RE: Jar-Problem extension installation

> Does the CLASSPATH environment variable of the unopkg call happen to
> contain some instance of that MidiCSDext.jar?

Yes it did contain an instance. After storing it away I no get:

/Applications/LibreOffice.app/Contents/program/unopkg add -v -f
MidiCSDext.oxt 
Copying: MidiCSDext.oxt
Enabling: MidiCSD
 Enabling: types.rdb
 Enabling: MidiCSDext.jar

ERROR: (com.sun.star.deployment.DeploymentException) { { Message = "An error
occurred while enabling: MidiCSDext.jar", Context =
(com.sun.star.uno.XInterface) @5a1331c }, Cause = (any) {
(com.sun.star.registry.CannotRegisterImplementationException) { { Message =
"", Context = (com.sun.star.uno.XInterface) @0 } } } }
 rollback...
  Disabling: types.rdb
  rollback finished.
An error occurred while enabling: MidiCSDext.jar

So I still have something wrong but, what?

Thanks,
  Martin