Index: wp-includes/pluggable.php
===================================================================
--- wp-includes/pluggable.php	(revision 18627)
+++ wp-includes/pluggable.php	(working copy)
@@ -74,6 +74,11 @@
 function get_currentuserinfo() {
 	global $current_user;
 
+	if ( ! did_action( 'after_setup_theme' ) ) {
+		_doing_it_wrong( __FUNCTION__, __( 'Current user information is only available on <code>init</code> action or later.' ), '3.3' );
+		return false;
+	}
+
 	if ( defined('XMLRPC_REQUEST') && XMLRPC_REQUEST )
 		return false;