SpaceChem: Why can't I advance to the next level?

I recently beat a level in SpaceChem (I feel like I need a cigarette after I beat one - and I don't smoke!) and I was met with the following unpleasantness:

SpaceChem screenshot

Why can't I select the next level? Did I forget to do something in the prior one? Is this a bug?


You need to solve Molecular Foundry first. I hit the same thing. That level is hard.

The level you can't get to in the far right there is actually the last level on the planet.