6.4 works with service pack 1 so that shouldnt be a problem. What would be a problem is if that OMS error comes up under a PC. OMS is a mac protocol so it should be no reason why windows will give you that error.......well....You know what? I saw ONE instance of that error on a pc (mine) and it was caused by yamaha's midi application (the one that comes with the motif es).
Give us more info about your computer (what OS you use) etc etc etc.
:hgk: