Manos,
There's currently a bug in Facebook's case tracker about (I believe) this issue. Basically, some apps can't post to the news feed with links or images. It's a bug on there end, and nothing we can fix on ours. Can you try removing the link to see if that works for you. You can always put a link in the message itself, though that's not a great solution.
developers.facebook.com/bugs/151722701585098
If you still have issues without the link/image, let us know. Otherwise, I'd monitor the bug report above.. hopefully, it will be resolved soon.
Thanks,
Alex