每一步都是按正确的流程走的，就是到最后点Download那个小圆钮的时候它会说
The download session has expired. Please click here to start the download again.
Possible reasons:
The download takes to long to be saved.
For this download, in the background your Internet Service Provider has assigned a new IP address. If you are for example an AOL customer, or use a similar Service Provider, please try to use a different browser.
If this problem persists to exist, you may want to purchase a Premium Account. As Premium users are not checked against their IP address, this problem will not occur. Or your internet connection is too slow to download the complete file within the session time.
浏览器用的是IE，没有使用代理
