I've traced a problem to Sonitus Reverb. I like the sound of the FX but I occasionally have an issue with it popping, peaking the output meters and wreaking general havoc on the audio. It seems to happen mostly when I increase/change the pre-delay/room size or diffusion when playing a song. I've stopped using it for the most part. It seems to be ok if I change the setting while stopped but what fun is that!? Is it just a temperamental plugin? I can't associate it to anything else I mig