So glad I'm not going mad after all. Have a virus that works with laptop but not iMac. Couldn't figure it out, then I found this. My experience is consistent with the above. The machine it works on is an earlier version of logic 10.2 I think. 10.4.6 is a no go. Look forward to a fix. It also means I can't use the Virus with Omnisphere ATM either 