Check to make sure the Java plugin is enabled under add-ons. Firefox likes to automatically disable old insecure versions of Java. Probably best set to 'ask to activate'. If it's whining about security, do the steps that yanbu posted on the main page. Also make sure that you're allowing 3rd party cookies under privacy settings. For a while at least, there was a weird bug where without that the drawr wouldn't post, even though 10e doesn't use any such cookies.