Sorry if this has been talked about, but I thought this problem was in the 2.40
Anyway I almost lost a scene I did a awhile back, when I was appending a tree from it to a scene I was working on today.
I hit the save hotkey about every time a make a change I like in a scene and I usually hit it a lot.
After I had appended the tree I hit Ctrl-S and it complained about not being able to save. I looked at the top where the name is displayed and it was the name of the file I had appended from. If I had not had both scenes opened I would of surely lost some hard work.
Why did it rename my file to the one I got my tree from.
At least I can watch out for this problem in the future, but this was a close call.
Did I mention that I love ambient occlusion.