Reply to Spectra - Changing banks causing feedback

I'm having a problem. Lets say I create a new track in a fresh Ableton set, load a clean synth (no effects), and start playing some notes. That's all fine. When I move to another bank of notes, the side-button creates a sound, and then feedback starts building with every button-press thereafter. Changing to a third bank causes the feedback to reach intolerable levels.

The only way to stop it is to unarm the track and wait a second. This does not happen when using a drum rack, nor does it happen with my MPD32. This problem also occurs in MuLab with the Spectra, at which point I have to restart the audio engine. Any suggestions?