Hi, you're on the right track,i had same problem,couldn't fix for weeks! and then i found that it was extensions conflict.So the solving is to reselect Mac OS base extension set, and enable all Digi,OMS extensions,USB,duplicate the set, make it "PT le", and error type is gone.Maybe you'll have to do this twice or more,as for me it stays stable for a while now. Ongaku. 