Thanks, both, for the input and suggestions.
LBH, yes, I did all of those things (thank you!), with no success. Actually, that's not quite true. I did get the Keylab working at one point and then the Keystep, but then I would add something else and the whole thing would fall over. I came to the conclusion that it was USB MIDI confusion of some sort on my main PC that was doing this, as I managed to get all devices working together without issue on a laptop. That, to me, discounted the devices as being faulty, likewise the cables.
So, from reading MajorFubar's advice (thank you!) I noticed that Windows had updated that day (I know, I know - I must turn that automatic update thing off!). So, I did a system restore to a point just before the update and bingo, I managed to get the Keylab, the Minilab and the Keystep up and running. But as soon as I installed the Beatstep Pro it fell over and all devices became unavailable. I restored again and all was fine until I added 'too many' devices. But before I started blaming Windows Update, I realised the laptop had been updated as well, yet was not causing problems. At least I knew there was a repeatable semi-cure.
What seems to have solved it for me (at least for now) was to do a 'repair in place' re-install of Windows. That way my apps and data weren't lost. I hadn't realised this was even possible, but it seems to have done the trick. Now I can have all devices running simultaneously. I think that doing the system restore got me thinking that it was adding one too many devices that was causing the problem, hence the repair in place of Windows.
It's now my (vague) understanding, having done a LOT of browsing for cures, that Windows has a limit on the number of MIDI devices that can be installed. Now, I didn't hit this limit in terms of the physical number of devices, but it appears that every time I was plugging in a device to a different port it adds a new installation instance. These don't go away after the device is physically unplugged. Given that I have 12 USB ports on the machine itself (those on the motherboard plus a PCI card) and I was adding and removing devices pretty much daily, I wonder if I had hit that hidden limit? Reading other sources online suggest that this is the issue as well. I think the Windows repair in place took me back to a clean USB MIDI state.
From now, I will reserve a specific port for each device and make sure not to use different ports. It's ironic that I was actually trying to establish a semi-permanent controller set-up when this all went wrong in the first place!
Thanks again for your input and I hope this long winded reply helps someone else who is enjoying the same pain.
Disappointingly, no input from Arturia or a response to my support ticket yet. I found other posts on similar subjects here that seem to have gone unanswered as well. I wonder if this issue is known to them? I would say it's well worth them looking into it deeply and coming up with some kind of resolution as it has definitely made me reconsider adding another device to my setup!
Cheers!
