I'm having a problem with the Mac version as well. I had gotten a song in RM format, which is supported by Switch, but when I tried to convert it to mp3, the pop-up just came up for one second and there was a big red cross next to it, and there doesn't seem to be any converted file in the output folder. When I try to double-click the file within Switch, it just says Mac doesn't support that type of file - which is why I wanted to convert it to mp3!