Hi Bob - there was a 32 bit Korg plugin in the project. I removed it and, as they say in separatist Quebec, le voila! no more clicking and popping!
but since you also asked, the I am using an Asio driver, 7.3msec I/o, 352 samples, 48khz sample rate, 2 buffers.
any advice on how to stop it from happening? is it just as simple as not using my 32 bit plugins? that would be a drag, as I love some of the korg stuff.