If you cannot to leave a comment to a post, try this
1) close all running browsers, open browser and try again.
or 2) go to the cookie management of the browser, looking for blog.bchinese.net cookes, one is called BLOGBCCN-SL, remove it, refresh the post, and then post message again.
It usually caused by your network problems.For example, if your IP is changed during a http session.