z3ta+ 1.5.3 - loud click, then no audio

This problem happens only with other banks other than the default.fxb bank that came with z3ta+ 1.5.3. The problem is: I load a different bank, listen to a few presets, then inevitably I'll hear a painfully loud click, and then I can't get any audio from any of the vsts loaded in the project (including z3ta+). I'm using Sonar 8 Studio. The problem happens with Sonar HS 6.2 as well. I end up having to close and reopen Sonar -- without saving my project. If save the project after the dreaded "click", I don't get audio even after I close and reopen Sonar.