...then suddenly stops...even from SD.
The SD card may well be your problem. The whole Squeezebox series was originally designed as a "network player", not a standalone device.
It works best with LMS (the server program) installed on a well configured, stable PC.
I've used Squeezebox players for 10 years (starting with the original SliMP3 to the Touch I have now) and never once had the system just stop while playing music.
Sounds like you you have a double-whammy. Nominal computer experience combined with trying to use the unit in its least optimal configuration.