Matt,

>What exactly does not work?  Is it not going into sleep, or not coming


It was a picMaster trick.
I use to leave my PCs on.
I've noticed, facing a strange picMaster behaviour I must restart the PC (ON/OFF
 supply).

After that, sleep operate perfectly well, even with external clock setting...

So, now, we're shure : picmaster 17C44 probe has sleep mode ;-)))

Friendly regards from Oleron island - France.

Stephane.