-have a java app which is set up also at facebook developers corner (or however it is called)
-d'n'd services tab -> web services -> Facebook -> SocialNetworkingService -> ... -> authCreateToken
-fill in required stuff in facebooksocialnetworkingserviceauthenticator.properties
-run the project
-authenticate your app in a browser and close the FaceBook Auth. Dialog

=>
...
run:
java.io.IOException: Failed to get a valid session secret.
        at
org.netbeans.saas.facebook.FacebookSocialNetworkingServiceAuthenticator.getSessionSecret(FacebookSocialNetworkingServiceAuthenticator.java:72)
        at
org.netbeans.saas.facebook.FacebookSocialNetworkingServiceAuthenticator.sign(FacebookSocialNetworkingServiceAuthenticator.java:170)
        at
org.netbeans.saas.facebook.FacebookSocialNetworkingService.authCreateToken(FacebookSocialNetworkingService.java:62)
        at javaapplication1.Main.main(Main.java:23)
BUILD SUCCESSFUL (total time: 22 seconds)

problem seems to be that generated FacebookSocialNetworkingServiceAuthenticator.java is looking for <secret> element
returned by facebook.auth.getSession but such element, as per
http://wiki.developers.facebook.com/index.php/Auth.getSession, is not guaranteed to be returned[1] - currently the
response from the server contains only "<secret/>" element (which is also bad, because FSNSA does not accept this as a
valid response).

[1]: see also http://api.facebook.com/1.0/facebook.xsd :
...
<xsd:complexType name="session_info">
  <xsd:sequence>
    <xsd:element name="session_key" type="session_key" />
    <xsd:element name="uid" type="uid" />
    <xsd:element name="expires" type="xsd:int" />
    <xsd:element name="secret" type="xsd:string" minOccurs="0" />
  </xsd:sequence>
</xsd:complexType>
...