Hi stuart,
We just released an update of the VC4 (available through the ASC) that should solve your issues.
Just to let you know, it was a combination of two specific behaviours of the previous version:
1. When two (or more) MIDI controllers were enabled in our plugs, only one of them was able to communicate with the soft. This was a Juce related issue and it's fixed now.
2. In Analog Lab, all MIDI controllers are enabled at the software startup, by design, since the version 1.1. This, in order to facilitate the setup for the new users of Arturia's products.
As I said, the behaviour #2 exists since Analog Lab 1.1 (about a year ago) and did not cause any issues. But this behaviour combined with the bug #1 forced the users to setup again the MIDI settings at each Analog Lab restart (disabling all the MIDI devices except one). I understand it could be really annoying..
This should be fixed now, feel free to repost here if you still experience MIDI devices related issues.
Best