Ubuntu – Audacity playback speed much too fast, on Ubuntu Mate 15.04

I just had a major issue with Audacity, on the first Ubuntu Maté distro. I was doing some sound work, and recording directly from microphones and audio monitors; but when I attempted to play back the sound, it was consistently done at an extremely high pace. Further experiments uncovered that even generated sound, like tweets, was playing back maybe 10x too fast—I could see it on the time bar.

Since I didn't really have time to mess around with it, I tried just uninstalling it, deleting all config files, and installing it from scratch. It works now, at least for the time being (thankfully!), but does anyone know what could have caused this? I don't really understand where the problem was coming from, so there's a good chance I'll see it again.

Thanks for all of your time and expertise!