Thank you bobruz!! After reading your post. I did some more thinking, testing and reviewed my midi settings. I was able to send midi PC from the PC+ to the Eventide H9 with no midi in from the helix. that gave me hope and in retrospect, looking at my Helix/PC+ midi settings it "kind of" makes sense now. I found either turning midi PC receive on the Helix off (which I don't need...not changing helix PC via midi) OR turning midi PC send off on the PC+ (in powercab edit system tab...which I also don't need) solves the problem. And leaving midi thru on allows me to control the H9 patch changes with PC+ preset changes from the corresponding helix preset change. It's peculiar, possibly a bug(?) and certainly not intuitive that the helix "midi receive" on (especially with nothing connected to helix midi IN) affects the helix Midi OUT especially since the behavior is locking up the PC+. I would not expect "midi pc receive" on to have any affect on anything other than the Helix midi in connection but alas, that is not the case. I don't recall but I'm guessing the midi PC send on the PC+ that died was turned off, I changed nothing on the helix and the behavior was different on the replacement PC+. Since I'm using the midi thru on the PC+ for simple H9 PC messages and no other midi connected devices, leaving the PC+ midi PC send off AND Helix Midi PC receive off works fine for my configuration.
So, Thanks again. It made my day. I was getting cold feet with the PC+ after a HW failure with the first one in the first two weeks (I repaired consumer electronics and musical instruments for over 15 years in a previous life and understand the failure rate of a new device is obviously higher than one that's been reliably "burned in"...that's why we have warranties) so that was luck of the draw it seems. With the midi problem on the new one, I immediately leaped to another HW failure especially since I was incorrectly assuming the config was identical with the one that worked (for a while). And was dreading the whole process of boxing/exchanging/replacing/shipping/whatever again. It's good to hear you've had no other issues. It's restored my confidence in the helix/pc+ set up. Thanks Much and Happy Holidays to you too!