It's a bug with Facebook that was recently introduced. There's not anything we can do to get around the issue, it's something that will have to be fixed by Facebook itself. The bug report for it is on the page below:
developers.facebook.com/bugs/280811108698311
We'd recommend using the "Does this repro describe your issue" link to add your information to the report. The more users that do this, the higher priority it gets and the more testing Facebook can do when a fix is available.
Hope that helps, and sorry for the troubles,
Alex