Permadeath

Whatever it was, it was fixed when I reset the controls!

I just got the game and it it seem quite fun, although I die quite a bit! However, the game have started behaving kind of strange. Whenever I click the left mouse button, it deselect the current slot and select the rightmost slot instead. Also, the rightmost slot have a "Left Mouse" text over it. What's going on? Is this a feature of some kind?