How to remove custom images from twenty ten

I’ve uploaded some custom images to the twenty ten theme and have the header set to show a different image on each page. I’d like to remove one of those images, but there’s no apparent way to do that. I can remove the image (and each version of that same image) via ftp, but that leaves a blank in the selections. That header image can still be randomly called, and when it is, it just shows up blank. When I click on the “Remove header image,” it doesn’t work, it just perpetually shows a “Save changes” button each time.

This is a little frustrating, and I can’t believe I’m the first person to run across this problem. However, I’m not finding much help when I try to google the problem. Can somebody point me in the right direction? Thanks in advance for your help.

Here’s a screen shot just to clarify things.