I have the same problem with Facebook Feed 0.2.3-beta.
I've created a Facebook app, entered the AppID and App Secret, updated the access token under Manager > Components > Facebook Feed. Added the snippet call with my retrieved Facebook personal numeric ID in. Also tried creating a new Facebook app but still get this error in the log:
/Users/xx/Projekt/mamp_dev/core/components/facebook_feed/model/fb_feed/feed.class.php : 222) Graph Error: Invalid OAuth access token signature.
Nothing is displayed on the page.