Hi guys,
I had an and I tested lots of commands from the console, formatted several time SDCard and so on.
Until I realized the following: it seems that using the commands "reboot" or "halt" from the console makes RuneAudio stops completely to work with my external sound card. From the GUI, I can see the song progression but I get no output. However, it seems to continue to work for HDMI output. Rebooting from the GUI did not help.
I solved the problem only with a new installation of RuneAudio, and using only the RuneAudio GUI to halt or reboot.
I am happy to conclude that updating Archlinux or adding a partition on the SDCard with my music was not the problem.
EDIT: the sound card was just muted after restart. See below.