During the course of testing our latest game, one of our producers had the game freeze right when the loading progress bar reached the 100% state. He already had Unity installed on his machine and wondered if a new version was needed. He verified that an older Unity game still worked in his player and then manually installed the latest web player and tried the new game again. It worked. So, it seems something went awry with the auto-update functionality in the player.

I'd like to try to reproduce this, but need to install an older version of the web player. Where can I find older versions?