Bosse,
We've never seen or heard of that error, and couldn't immediately tell you what's causing it. I see you had a subscription that ran out in April. Not sure what version you're using, but Facebook does change things on their end regularly, which we always keep our releases in-sync with. If you're on a release before 3.2.x, we'd first suggest upgrading.
If I knew the answer to your question, I'd gladly give it to you, but beyond the recommendation of upgrading, I'd need to see the page to understand what's happening more.
Thanks,
Alex