When i used the simple facebook login for Android which i made a few days ago i didn't have this prolbem.
Now when i run the app i get an "invalid key" - "Android key mismatch"
06-07 02:08:51.104: W/GET_MESSAGE(273): invalid_key:Android key mismatch. Your key "Es2Fbgrno9htovlX6FcXiex6u0I" does not match the allowed keys specified in your application settings. Check your application settings at http://www.facebook.com/developers
![api-key] http://imgur.com/8uTnu
And here is the wrong key i get from the Android app :
![wrong-key] http://imgur.com/TCD5k
The key that i get from the app as an error is different from the key i have declared in Facebook developers