To the anonymous person with the MOTU interface: we have examined our customer support logs, and can find only one report of a stability problem, that also happened to concern a MOTU interface, and that was long enough ago for that customer to presume an upgrade wouldn't be free. We considered the issue resolved, because we never got a reply to our response. That customer purchased Mac the Scope 4.0 (4.0b1 doesn't exist); and that purchase also qualifies for a free v. 4.1 OS X upgrade (it was made after October 1, 2002). In fact, we have already sent out free 4.1 activation codes to all customers with valid email addresses on file. So that's one down, at least (and might be two if you try 4.1 with your interface). If this doesn't describe you, then you have been silent about your trouble, and so it's difficult for us to help. We are sincere about helping customers to use our products, and your comments convey an impression that I believe is contrary to the experience of most of our customers. I would be happy to continue this discussion with you via email or telephone support (please see our website for contact information), and look forward to hearing from you, at your convenience.