I have the same sending problem.
The problem occurs on a windows 2003 box using IE7, Firefox 3, Google Chrome, Safari 3.1.2, Opera 9.01
I have break on script error i IE, and I get the following errors when I try to compose a message, and send it:
Script error 1:
on entering compose page:
error: Line 2047 (i assume it is in app.js)
if (editor = tinyMCE.get('compose-body'))
Object doesn't support this property or method
Script error 2:
on pressing "Send" button:
error: Line 1982 (i assume it is in app.js)
if ((!window.tinyMCE || !tinyMCE.get('compose-body')) && input_message.value == '' && !confirm(this.get_label('nobodywarning')))
Object doesn't support this property or method
I do not seem to have the same problem on a vista machine running ff3 (although that could be a caching issue).
Royan