Facebook changed some things.
They have a new sdk which the script needs to connect.
To resolve the problem:
a) Your server should run php 5.x - otherwise it will not work.
b) Download q2a Version 1.5 and copy the folder .../qa-plugin/facebook-login
to Your actual plugin folder. Make acopy of Your old login-folder first.
Thats all, it should work again without problems.