Ultimate Facebook cause Varnish to not cache anything

Hi, I have a wierd problem on one of my sites.
When the Ultimate Facebook plugin is network activated, the Varnish server infront of apache will not cache anything (constantly Age: 0).
If I deactivate the plugin and restart Varnish it will start cache'ing again.

My vcl

# Marker to tell the VCL compiler that this VCL has been adapted to the
# new 4.0 format.
vcl 4.0;
import directors;

# Default backend definition. Set this to point to your content server.
backend default {
    .host = "127.0.0.1";
    .port = "8080";
}

acl purge {
    "localhost";
        "127.0.0.1";
}

#sub vcl_recv {
    # Happens before we check if we have this in cache already.
    #
    # Typically you clean up the request here, removing cookies you don't need,
    # rewriting the request, etc.
#}

#sub vcl_backend_response {
    # Happens after we have read the response headers from the backend.
    #
    # Here you clean the response headers, removing silly Set-Cookie headers
    # and other mistakes your backend does.
#}

#sub vcl_deliver {
    # Happens when we have all the pieces we need, and are about to send the
    # response to the client.
    #
    # You can do accounting or modifying the final object here.
#}

sub vcl_init {
  # Called when VCL is loaded, before any requests pass through it. Typically used to initialize VMODs.
}

sub vcl_recv {

                if (req.method == "PURGE") {
                    if (!client.ip ~ purge) {
                      return(synth(405,"Not allowed."));
                    }
                    return (purge);
                }

                if (req.url ~ "\.(gif|jpg|jpeg|swf|ttf|css|js|flv|mp3|mp4|pdf|ico|png)(\?.*|)$") {
                unset req.http.cookie;
                set req.url = regsub(req.url, "\?.*$", "");
                }

                if (req.url ~ "\?(utm_(campaign|medium|source|term)|adParams|client|cx|eid|fbid|feed|ref(id|src)?|v(er|iew))=") {
                set req.url = regsub(req.url, "\?.*$", "");
                }

                if (req.url ~ "wp-(login|admin)" || req.url ~ "preview=true" || req.url ~ "xmlrpc.php") {
                return (pass);
                }

                if (req.http.cookie) {
                    if (req.http.cookie ~ "(wordpress_|wp-settings-)") {
                        return(pass);
                    } else {
                      unset req.http.cookie;
                    }
                }
 }

# Drop any cookies Wordpress tries to send back to the client.
sub vcl_backend_response {

        if ( (!(bereq.url ~ "(wp-(login|admin)|login)")) || (bereq.method == "GET") ) {
        unset beresp.http.set-cookie;
        set beresp.ttl = 1h;
        }

        if (bereq.url ~ "\.(gif|jpg|jpeg|swf|ttf|css|js|flv|mp3|mp4|pdf|ico|png)(\?.*|)$") {
            set beresp.ttl = 365d;
        }

}

sub vcl_deliver {
   if (obj.hits > 0) {
     set resp.http.X-Cache = "HIT";
   } else {
     set resp.http.X-Cache = "MISS";
   }
   set resp.http.Access-Control-Allow-Origin = "*";
}
sub vcl_hit {
  if (req.method == "PURGE") {
    return(synth(200,"OK"));
  }
}

sub vcl_miss {
  if (req.method == "PURGE") {
    return(synth(404,"Not cached"));
  }
}

Is there something in the vcl that could cause this or might it be something in the plugin?

Thanks
Tomas