WYSIWYG not visible

I upgraded a test blog to 2.1. It worked fine. I then upgraded a second blog to 2.1–both from 2.07. Both are working fine.

Then I installed a new blog with the 2.1 download, and everything seems to be working fine except for one thing: the write post/page does not show a WYSIWYG editor. It only shows the “CODE” menu. I double checked the other two blogs and both editors are visible and clickable.

So, the only difference here is that one is a new install with 2.1 and the others are an upgrade with 2.1. So something must be missing. Any ideas?