Attached is the sub-vi that works now. Never had this happen before.
The reads/writes to the Agilent supply take an inordinate time to complete. I had to move the V and I indicators out of the sequence an wire a local read in the idle condition in order for the values to be displayed.
Now this is the embarrassing part: it's highly likely that the supply was responding to the write commands all the time, and simply not enough time was given to read the values in the next loop iteration. The supply front panel is not easily viewed from the pc. It was probably going to voltage during all this headache but I never checked!!
So much for 'assumptions'
Thanks all for your help and suggestions...and patience.