No, the same behavior. It can't find the file.
I suppose I just have to try creating one, cross my fingers, and hope it works?
I just created a new particle exactly like one I created earlier and it seems to work. But about ten minutes after creating it, all the others disappeared. I didn't delete them, just some unexpected behavior from MC.
Another data point is that the particle that worked has a file path that pointed to the original .wav file. The "bad" ones had a file path that pointed to a new .wav file in the same folder as the original. For instance, if I named the particle "Track1" the file path would be .../Music/Album Name/Track1.wav. Of course, that file did not exist.
When you're looking for the bug, that's most likely the place to look.