In Dashboard \ Global I see a list of blogs on the system. Under the "P. List" column is a list of publicly visible blogs, each one with a black / filled in circle, signifying a visible blog. When I try to click one of those circles to hide a blog, I get:
Init objects: unhandled action
in a pink background. I'm not sure what causes this.
EDIT: Same error in all 3 admin skins, so I don't think it's the admin skin itself which is causing this.
After working on some other parts of the site like taglines, etc, I came back to this and it suddenly worked. I hadn't changed any core settings in the blog except for things like category names, taglines, footer content, etc. It's some kind of transient error and I can't figure out what's wrong. Even enabling debug mode didn't show anything obvious.