any JS errors? are you using any other plugins?
Not seeing any JS errors in the FF error console.
As for plugins, the list from main.inc.php:
// List of active plugins (in plugins/ directory)
$rcmail_config['plugins'] = array(
"compose_newwindow",
"compose_addressbook",
// "contextmenu",
"calendar",
"pw_recovery",
// "markasjunk",
"markasjunk2",
"jqueryui",
"forwardattachment",
"globaladdressbook",
"sendmessage",
"message_highlight",
"sauserprefs",
"sticky_notes",
// "vacation", // Need to edit & make it work first!
"automatic_addressbook",
"keyboard_shortcuts",
"emoticons",
"session_timeout",
"sieverules",
"searchbox",