Rich,
That looks to be a bug with our new version of JFBConnect. When you use the Enable Debugging setting in JFBConnect, we change a lot of things that we output into the page, and it looks like the Error Checker tool hasn't been updated with all the proper checks.
We'll fix that in our tool soon, but for now, to run the Error Checker, set the Enable Debugging setting in the Configuration -> Misc area.
I hope that helps, but if not, let us know.
Thanks,
Alex