I've been having this happen quite often... when I stop a song and it returns to the beginning on the song editor, the tempo resets itself to 140. With some projects it happens, with some it doesn't... I haven't imported any midi files into any of my projects, only wav files, I still haven't been able to work out what it is that I'm doing that triggers it to reset. I'm a new user of lmms ( and loving it so far ), so sorry if this is a noob question!
If you havent imported midi, the best candidate would be an accidential change in the 'song global Automation'
Rightclick the TEMPO/BMP, chose 'song global Automation' and check for that.
b.r.