Ok, I explored the situation a little further and come to the temporary conclusion that it's a software problem.

I'll try to describe the problem again, little better:

1. everything's up and working as expected
2. I shut down windows, the Fireface keeps the settings as expected
3. on rebooting windows, as soon as the red host led turns off, a standard configuration is loaded (different from last settings)

I have de-/reinstalled the driver already, flashed the settings (reading flash works) but still: there's a FF settings preset loaded of which I believe it's the standard one (256 samples buffer, Inputs 1, 7 + 8 set to rear, Phantom power off etc.).

Where else could I look into to make it keep the settings?

Thanks, that does the trick to a certain extent. On reboot the FF settings are loaded which were active when I hit that 'Lock Registry' button.

Not the last state when quitting windows though - which was the usual behaviour since I use FFs (and that's for many years meanwhile). Still don't understand what causes the change on my system as I'm not at all conscious about any change I've done in this regard HeadScratch