EDIT: the work-around below did not correct the sound problem my wife ran into. Halp!
Original over-optimistic post:
My wife had a problem where the main music had harsh sound near the end of its loop, and I theorized that the sound file had somehow been corrupted. I had to Google around to find out how to fix it, and now I'm posting the instructions here so they can go in the FAQ or something:
1. Exit Ur if you're currently playing.
2. Go to Adobe - Flash Player : Settings Manager - Website Storage Settings panel
3. Find the sites with "glitch" in their name and Delete them (we deleted all sites when we tested this so we don't know which one(s) matter(s)).
4. Re-enter Ur.
If anyone knows an easier way they didn't come up near the top in Google. :)