When I send one to one emails I get a security error. Sometimes it comes and goes. Not all people using my instance of NationBuilder are getting this error. It either prevents emails from sending or sends emails without recording activity in the Control Panel.
Thanks Lem! This happens sometimes when a window is open for a while before you send the email - usually if you hit back on your browser you are able to get the content of your email back.
Although it sounds like this is happening more frequently for you. I will let you know if there are any updates.