If the EZ250i is connected to the computer, and the game won't start, the Yamaha USB MIDI driver has probably not been selected as the preferred MIDI Music Playback Device in Windows.
For Windows 98/ME:
Browse to My Computer/Control Panel/Multimedia/MIDI.Select 'Yamaha USB OUT' as the default MIDI device.
For Windows 2000/XP:
Browse to My Computer/Control Panel/Sounds & Multimedia/Audio/MIDI Music Playback.Select 'Yamaha USB OUT' as the default MIDI device.