Your robots.txt file really shouldn't matter. It can be used to block automatic bots from scanning your site. While the webmaster tools shows the jfbconnect.js file blocked, that's ok... the google bot doesn't need to execute any code in that file. You shouldn't need to make any changes to your robots.txt file for normal JFBConnect operation.
I hope that helps explain, but if you need any other assistance, please let us know.
Thanks,
Alex