ok --- this may not be typical usage (grin)
I had opened AudioMulch and started working on a simple sequence patch.
At the same time, I had QtCreator open and I also had Xcode compiling the entire Juce library.
I quit AudioMulch (or tried to) after saving the patch but AudioMulch did not close properly and even a Force Quit wouldn't kill it off completely. Soon thereafter, Xcode got stuck as did a few other apps.
I can't say for sure that the problem was DUE to AudioMulch but I've never had this happen to me before.
Running OS 10.5.8
I now think this was a red herring --- it's starting to look like the problem is due to Xcode trying to build lots of objects concurrently on a remotely mounted file system (which is something I had NOT done previously).