近来项目需要学习起flex，利用FileReference进行上传文件的试验。结果总是报告#2038错误。
查了很长时间，总算在这找到了不少的提示
IO Error #2038
http://swfupload.org/forum/generaldiscussion/92
其中一段是这样说的
Flash IO Errors are not very helpful. The same couple of error numbers are returned for just about everything.
Here are some common issues that cause these error codes:
- Invalid URL
- Server max post size or max upload size exceeded
- Server unexpectedly terminates the connection
- Zero byte file uploaded
- Basic Authentication failed
To debug these issues I first verify that my upload is working using a standard HTML upload form pointing at my upload.php
说Flash的IO错误提示不是非常有用。几个错误码就包含所有的错误信息。跟着列了IO错误通常包含的错误，并建议我们先用html原上传方式确保上传的页面没有错误。
结果真是我的up.aspx有错误引起的。