New errors... for no apparent reason?

So I got back to my project after a few weeks hiatus and decided to work on it. However, when I launched Unity, I got these compile errors.

It worked fine before I shut down Unity last time I worked on it. Now suddenly I get these strange, unspecific errors. Anyone know what this is?

The NewLevel script errors are specific and tell you exactly what the problem is and where it is. The mesh inertia tensor error is usually the result of trying to add a rigidbody to an open mesh collider; don’t do that.