Our current release-20130514 installer will no longer work reliably on Windows.
You can work around this problem by installing OpenAL manually, or by installing the release via Desura.
The problem occurs when the installer detects that OpenAL is missing, and tries to download the installer from Creative Labs. Their website has been taken offline, and it appears unlikely that it will return.
A new release will be out within the next week or so that fixes the installer and adds a huge number of fixes and improvements. If you’d like a preview of what’s to come, you can try the playtest-20130908 build from the downloads page.
We are also preparing a brand new website, which will be deployed with the new release.
This new website will be much easier to for us to update and maintain, so we will begin posting playtest news (which was previously only posted on our ModDB page) to add a bit of life to our oft-neglected website.