Views module - can't expose my filters

I'm using Views to make a block that shows recent stories in a vocabulary from which I want the user to be able to select a single term. I am using the "list" format in this block and listing only the node title, as a link, sorted by original post date descending. Pretty simple.

The filter I have created in Views edit works fine, but even when I click Expose and save the view successfully, I don't see the exposed vocabulary filter when I check the block on the site -- just the results of the filter as set in the View itself.

To see if I'm just messing up that particular filter, I also tried to expose the much simpler "promoted to front page" filter, and that won't expose in the block either.

I am testing this block with "administrator" only privileges so the results of my tinkering are not visible to live users other than myself, but that should not be a problem, should it?

In this installation, I've successfully exposed filters by accident before, when toying with a view, and now that I want to, I can't. Is there something obvious I'm missing?

Thanks