Block config on some pages result in settings you can't undo, and undesirable pagetype/context settings

I am trying to customize the blocks that students will see on their user profile page. I go to Settings > Site Administration > Appearance > Default profile page and click the "Customize this page" button. Then, I add a block. If I leave it as-is, it works fine, and appears where it should. But if I can go into its settings to edit its page context, strange things happen. The first time you access it, there are two choices under "Display on page types": "Only user profile pages" and "My home page." The SECOND and all later times that you return to those settings, a third option "All pages," has appeared.

What is problematic is that, once "All pages" has appeared, the block's "Display on page types" ALWAYS defaults to this, no matter what setting I choose. If I change "Only user profile pages" (see image "beforesaving.png"), and then press "Save," the setting is actually immediately reset to "All pages" (see image "aftersaving.png"). I cannot figure out why the setting that I apply won't "stick."

I have replicated this problem on both our local Moodle 2.x installation and on demo.moodle.org.