Hi there,
I really need to solve this to get some stuff done. I always have the same mic/audio interface in the exact same USB-Port. Sometimes after loading there comes a notification box up that my configuration has changed(it has not) and the audio selecting box comes up. It finds the same configuration as always. But now in that project recording is impossible. I can already see this when arming a track: it stays all grey. When it works, there always comes a small green dot in the mixer/volume panel.
When creating a new project, recording always works so the setup is alright, no hardware problems. But I am always loosing all my progress when this comes up and I need to start from scratch.
How to get the old project to be able to record again? It shows the right device but i can arm whatever I want, no recording is done at all 
Greetings and thanks for any help in advance.
Having the same problem on two different computers, on ubuntu and archlinux. So I guess I am doing something wrong in ardour? But I have no clue what it is.
Maybe this information is important: using ALSA.