Recently, I had some issues with not being able to use Message Walls. I could load the page, and type a message, but the actual proper editor wouldn't load and there were no buttons to post or reply. A fellow user mentioned having the exact same problem and said that he was able to fix it by uninstalling his Java (which was Java 6) and upgrading to the newest Java, Java 7. This was apparently after a lot of frustration and being told that the issue was specific to his computer, so based on it happening to me as well, this is definitely a Java issue.
So if you're having any problems with this, visit [www.java.com/en/download/manual.jsp Java's site] and here you'll find the download for the newest version. Just do what I did - download the new version, then close your browser, uninstall the old one and update to the new one. You should be good to go.