On several Macs now running OS 10.2.3, and mBox with PT 6.0 or 6.01, we have had an issue, where the mBox does not have any output ( barring a very quiet crackle). systems; iBook 600 iBook 700 Powerbook G4 867 12" All systems 10.2.3 All systems more than 512mb ram Always logged in as administrator System settings as per install procedures. Repairing disk permissions does not solve the problem Unplugging the mBox, then plugging back in and relaunching Pro Tools seems to solve the problem, until the next reboot of the machine. Does anyone have a definitive answer to this issue?