We found that the installation of certain Logitech web cams under Windows XP prevented Mixcraft from recognizing MIDI data. The fix for this problem requires that you edit your Windows Registry, so don't attempt it unless you're comfortable doing that.
1. Click on the Windows Start menu, select Run and type in Regedit.
2. Find the following key:
3. Delete the UpperFilters and LowerFilters value from this key. In some cases you might only have one or the other.
4. Uninstall the USB audio device, unplug it and plug it back in again.
5. The problem should be fixed!