Redline EQ plugin problems

[JKC]

I've been using Redline EQ as a VST plugin in Izotope RX Advanced with no problems.  Now I have a client who wants me to clean up a Final Cut Pro project, so I want to use the AU version in Soundtrack Pro.  Using it in a multitrack project, everything seems OK when I play the tracks, but when I export the mix I get a garbled sound -- sort of like someone trying to gargle water and talk at the same time.  If I turn off Harmonic Distortion, the problem goes away.

Next I tried using it as an AU plugin in Izotope RX Advanced.  This is a major failure.  After a few clicks on controls, the UI freezes up, and I have to force quit the program.

Any of the Apple AU plugins which came with Soundtrack Pro work fine in Izotope.

I'm a recent convert to Mac, so the only other program I have that supports plugins is Amadeus Pro.  When using the Redline EQ as an AU plugin, the UI works OK, but I sometimes get the same garbled sound I heard with Soundtrack Pro.  When that happens, turning off Harmonic Distortion fixes the problem; then I can turn it back on and it sounds OK.  Sometimes, it seems to work OK right from the start.

Redline EQ works OK as a VST plugin in Amadeus Pro.

My computer is a recent Mac Mini with 2.4 GHz Core 2 duo and 5 GB of memory, running OS X 10.6.6.  Total CPU utilization remains below 20% when running the plugin, and I've got plenty of free memory.

I know Soundtrack Pro is a brain-damaged program, but using it for this project does considerably simplify my workflow.  Any hints about how I might get Redline EQ to work as an AU plugin?