Update: There is a confirmed bug in the launcher that can result in corrupt downloads in a few specific situations, and this build is one of them! You NEED to use the "Validate Installation" button after you finish patching. This will correct the problem. Otherwise, you can suffer from weird random issues, including audio drop outs, crashes when loading into certain areas, and missing monster graphics.

We'll have a new version of the launcher ready soon -- in the mean time, when switching between this version and the "live" version, use the Validate Installation button to make sure your install is correct! (Here's how: when you see the "Play" button in the launcher, don't click it; instead click "More...", then "Validate Installation". When it's done, you're all set and can press Play.)

This apples to both Windows and Mac users. The linux launcher doesn't suffer from this bug as far as I know.