Glad you've got it working again, but I'm really surprised it didn't work in 10.5.5. But I don't know of any big advantage to using 10.5.5, so stay with what you've got until there are some more updates! I've been using it now for many days, and I've handled just about every parameter in MachFive2, creating big ensembles and little (even just solo instruments), and even played with the synth emulator and organ emulator (it's got the drawbars of the B3, plus percussive attacks optional using any harmonic!), and even running for long hours with screensaver occasionally coming up while I eat or do something else, it STILL doesn't crash. Saves just fine. Performances created in Stand Alone work fine in the plugin mode, and vice-versa.
Funny someone should mention the Streaming button. When I first got MachFive2 that button would almost always cause a crash. I messed with it the other day just to see if it would, but it stood firm. No crashing! That's 10.5.5, DP 6.01, M5.2.02, etc. It's also playing nice with Kontakt2 Player, Wallander WIVI, Ivory, MSI, and others, all loaded at once. I'm liking DP 6.01 very much, now that I've gotten past the crashy 6.0, and the bizarre and sudden change of the GUI. I still have not bounced anything to 2-track, but I'll cross that bridge in due time.
Good luck to all... I hope your stuff runs as smoothly as mine has been, and I'm knocking on wood about that.
Shoosh
