That's a fair question, Rob. I've actually done away with the block. Perhaps some history is in order...

When I was first testing these modules, and had a couple Facebook Apps running on a single Drupal, I needed a way to give each app it's own primary links style navigation. So my idea was to create a few blocks that are unique to each App. I used block 1 to create a hard-wired menu-style navigation for each app.

I was never really sold on my own idea, though. And I thought it would be much better to use menus for navigation, and not these weird blocks that I thought would be difficult to explain why they're there.

So, while I was making some other changes recently, I got rid of the blocks. I'm still not sure whether they're needed. Perhaps if you weigh in it could change the way things go. I was thinking, if these things are needed after all, of adding another module, fb_navigation, that would allow you to specify which menu is primary on a given apps canvas page, and perhaps also provide some custom blocks.

But to address your immediate need of fixing a typo. Edit your copy of fb_app.module. Look for /* XXX This needs to be re-thought... */ and uncomment that code. Then you'll be able to edit the block again. Sorry about that.