To emphasize the importance of doing a "save as" backup of your work,
and also to point out a potential bug, I offer the following tale:
I'm currently doing some drum program for a guy in VA. I'm working from
CD's he mailed me, and I'm using Doggiebox to fill in drums on audio
tracks that came off the CD's . I'm using Cubase to put things together
and check my programming.
The song I'm working on is just over three minutes long, and I had
about three or four hours into the programming. For no reason at all, I
played with the "Master Tempo" slider. I set it back to 100% then did
a save.
When I exported a wav file to check the patterns in Cubase, I noticed
an immediate problem with Tempo. I went back to DB, and saw that the
slider still read 100%. There is no chance that I exported while the
slider said anything other than 100%.
I was able to open a backup song file, then copy the changed patterns
from my (now bad) song file into it. Problem solved.
I think there may be something wrong with the way the slider works. I'd
advise "hands off" unless you know what you may end up with. Do a
backup.