No, it's an issue with Facebook itself. Their Javascript login button can 'jump' while it's rendering causing the problem you mention. To stop it, use the Login Button Type option in the SCLogin module and change it to Text or Image. That will hard-code the button to be either an image or text, bypassing the Javascript stuff. It makes the page load faster, prevents the 'jumping', and in general is what we recommend. However, it means you need to take or create a picture for the button and it's not multi-lingual compatible since the image won't have translate-able text.
Hope that helps and explains!
Alex