This error means that another extension, plugin or template on your site is including Facebook's deprecated all.js Javascript library. That is the 'old' version of the Facebook Javascript API which was discontinued about a year ago. It's no longer meant to be used and can cause conflicts with some JFBConnect features. Some common extensions that included Facebook features are JomSocial, EasySocial, K2. You will need to check your plugins, components and/or template for any Facebook features and try to disable them.
This should hopefully get you going, but if you still need help, please let us know.
-Melissa
Facebook Javascript Library Error
