I'm writing ActionScript game and wanted to integrate it with FB, so I used http://code.google.com/p/facebook-actionscript-api/ with custom dialog function I've found in same issue thread. It goes like this:

    protected function dialog(method:String, callback:Function, stageReference:Stage, stageWebView:StageWebView, params:* = null):void {
        dialogCallback = callback;
        stageRef = stageReference;

        webView = stageWebView;
        webView.stage = stageReference;

        webView.assignFocus();

        dialogWindow = new DialogWindow(handleDialog);
        dialogWindow.open(method, applicationId, webView, params);
    }

I've written module to handle all the FB stuff and it worked perfectly. But few days ago I've noticed that dialog shows up, but when I select friends and try to send apprequest to them i get error:

An error occurred with your app. Please try again later.
API Error Code: 2
API Error Description: Service temporarily unavailable
Error Message: User can't send this request: Unknown error

I've checked it, and found out, that after selecting friends and clicking send dialog changes location to http://www.facebook.com/dialog/apprequest, the error occures, and than after clicking "ok" it changes location to redirect_uri.

Do you have any ideas? Is this my fault or facebooks'?