I have tried to download and install Planeshift 0.3.20 (Windows) twice, and both times it has been corrupted. It was the German mirror, you should check it. That's no fun if one download lasts two hours
Now I'm trying it again, this time I use the Swedish one. Hope it works.
And by the way, the MD5 checksums for this release are missing on the download page.
EDIT: finally installed the game from the Swedish mirro