Sorry to hear about the recent issues you have been experiencing.
That message appears if you have two devices set up using the same MIDI port on the same MIDI Channel.
When you have two MIDI devices that may be on the port, make sure to set each to a different MIDI channel so there is not a port in use error message.
Options(Preferences OS X) > External Devices. Edit the instrument.
Please submit a ticket to technical support if this does not help resolve the problem. Thanks.