An AJAX HTTP request terminated abnormally 问题

使用 Form API 里面的 #ajax 属性开发发送验证码的功能，但是总是弹出 An AJAX HTTP request terminated abnormally 错误，要怎么解决啊？

以下是弹出的错误信息：

An AJAX HTTP request terminated abnormally.
Debugging information follows.
Path: /en/views/ajax
StatusText: 
ResponseText: 
ReadyState: 4