It has just frozen again a moment ago. This time the remote went off completely and the KPA froze in tuner mode. Still connected to Mac but with RM closed but this time the Mac wasn't in screen saver/sleep mode.
There seems to be something strange going on with the current OS as I haven't had a freeze for many months until recently. I guess it's time to email support.
I've had a couple freezes lately, same thing - connected to my Mac via USB but withOUT Rig Manager being open.