Opening the same score
1. Open a score.
2. Make a change.
3. Open the score again.
4. 'Cancel'.
Result: Two scores open.
Discussion: Should this happen? I'm not sure.
It might be a little far-fetched, but what about if you have a score open, the file name is changed, another file takes the name of the loaded score and you open it?
Using MuseScore 2.0 Nightly Build (3a23613) - Mac 10.7.5.