This is not JFBConnect. This is the exact same issue as reported before. In the following file:
/templates/socialize/local/css/themes/mytheme/template.css
At line 3481, is the following CSS style:
.modal-login .social-login {
width: 50%;
}
That is setting the button to 50%. That code is not in JFBConnect at all and not something we can control. I'm assuming you also updated your template at the same time, and that's where the issue came from.
If your template has a way to create overrides, I highly recommend doing so for the style above and forcing it to 100%. Not all templates support custom.css, so you'll need to contact your template provider.
Thanks,
Alex