Title Is Stored in the Database but Not Displayed on Page

I'm using the Ability theme. I've created blocks using Collapsiblock. One is placed in the left sidebar and two in the right sidebar, all of them collapsed by default. In the case of the ones in the right sidebar, the title of each block does not display. The little arrow that's supposed to be to the left of the title does display in Firefox, but not in IE7. I discovered that the link to expand and collapse the blocks does exist because I can see the mouse cursor change as I move the cursor over the area. When I click on the invisible title, the block does expand.

Digging a little further, I did find that the titles for the blocks are indeed stored in the "blocks" table in the database. However, when I view the source code for the page when it's displayed in the browser, here's what the HTML looks like for the block title:

{div class="block block-block" id="block-block-1"}
{h2 class="title"}{/h2}

(I've replaced the angle brackets in the tags with braces so that the HTML code will pass the filter in Drupal.) As you can see, the text that should be between the h2 tags is missing.

Other blocks on the page, that don't use Collapsiblock, display the title correctly.

I really like Collapsiblock. It's almost essential for Web sites that have lot of information to be displayed but want to minimize scrolling and page flipping. I sure hope you can get this one fixed quickly or give me some guidance regarding what I could do the work around the problem.