Do you have some MIDI interface with drivers? If so, if its only a midi device it might work without (unless the manufacturer was too cheap to add support for the generic USB-Midi protocol), try uninstalling any unneeded MIDI drivers, yeah. Also check Library/Audio/Midi Drivers in both the disk root and the user directory for any installed midi (hard or software) drivers.
Plugin latency issues? Phasing on parallel channels? Want to know the real latency of your audio interface? Try the VMG-01!
Professional Audio Engineer at Theater Bremen, Germany • Part Time Programmer