It may be a Mountain Lion thing, as it started about then. The developer's support has been limited to "uninstall and reinstall it". They won't help me much beyond that. And I've done that twice. The stand alone app works just fine. But Logic Pro is disregarding it as unsupported now. Yes, it did work when I originally purchased it. I have several music projects (fortunately my own private projects, not for clients) that have the M Tron on several tracks. Thus they're all at a stand still until I can get this working again. Anyone have insight or experience with M Tron Pro, Logic 9, and OS X 10.8? This is very frustrating.

Hey Ben, Have you tried M Tron with Logic running in 32-bit and 64-bit modes? Wondering if one or the other mode might work better?

I'm about to try that, but it worked quite well in 64-bit mode before. I'm going to give that a shot. Thanks!

I FINALLY got a realistic response from the developers tech support (after many months). I had to remove it and reinstall the recently updated installer for M-Tron Pro. Then launch Logic Pro in 32-bit mode, open the AU Manager, and see that M-Tron Pro was unchecked as not available. Check it, which allows me to force a re-evaluation of it by Logic. It was approved and works fine now. Quit, change Logic back to 64-bit mode, and then go back to work. The developer claims they are working on a 64-bit version of M-Tron Pro. Not sure why it is taking so long. I suspect they're developing for a future release, specifically. I'm crossing my fingers. Side note of interest; When I reinstalled M-Tron Pro and went into 32-bit mode and then into the AU Manger, something I've done several times previously, I was shocked at the number of plugins that suddenly appeared in the list, all being unable to load! Wow! Reinstalling M-Tron Pro triggered off something, obviously. Now I have to go through them one by one, and figure out what is what. Wow... At least this save six or more song projects that heavily relied on M-Tron Pro (and thus haven't been touched in over six months).