There were a few annoyances that crept into the previous version, so we have decided to release an update. This version fixes the error on loading, using spawn.txt in archives and using skyboxes in map archives. It also includes an updated lobby client. Full changelog here. This version is network compatible with 0.61b1, so you can currently join the lobby with the old version as well. But an upgrade will probably be forced next week or so.
If you have installed version 0.60b1 or 0.61b1 already, you only need to download the updating installer. To upgrade any other version or to do a fresh install you will need the regular installer.