Block For View Won't Allow Me to Set Its Display

I have created a basic node view. Overall, I am trying to provide a simple menu block that displays the last five nodes that have been added or updated, based on those respective dates. It is configured with node filters on type, of which there are about six content types selected, and the Published node filter. I also have two sort items configured, last update and post date. Within this view I have the default display and a Block display. The block display is defined to list the last five items. No "more" link. I am not using AJAX. No caching. The style is HTML settings, and the row style is Fields. I am returning a single field, Node Title, which is defined to display the title as a hyperlink. The live preview returns these values in a nice unordered list, which is what I want.

My problem is when I try to enable the block for this view. In the blocks admin page, I select to display it in the Sidebar left region, save the configuration. When I view the blocks list again, the block is still in the disabled list. I have tried moving it via drag and drop, as well as by selecting from the drop down list. I believe this to be an issue with views, as I am able to move other blocks around without an issue.

My question, then, is: Are my settings conflicting with the display of this block? Is there a setting I am missing? I have quite a large number of other view blocks on my site, defined as tables, and have not had this issue.

Thanks in advance.