Chrome や Firefox ブラウザなら問題なく投稿できる模様。
http://knownissues.blogspot.jp/2013/02/some-ie9-users-are-reporting-bx-lcbzu1.html
Some IE9 users are reporting bX-lcbzu1 errors when trying to publish. We're investigating the problem and in the meantime recommend you use another browser such as Chrome or Firefox.
