- There may be a conflict between the ATTO driver and the device driver being loaded for the peripheral.- Boot with shift key held down to turn off extensions. If the system boots, remove extensions one at a time to find and extension conflict. You do not need the ATTO Express Pro-Tools extension turned on for the application to work. - Also try refreshing PRAM. PRAM can become corrupted when changing the hardware configuration of a Macintosh. Hold down "Command-Option-P-R" while starting up the system. Continue to hold down keys until startup chime is heard three or times.