Suppose you quoted a message and started typing a reply. Then for some reason you had to leave it for a long time. When you complete the reply and try to send it, "the message has the following error or errors that must be corrected before continuing:" warning appears without any explanation. I am not sure about the session length. I will try to replicate this on my local install and report back.
Yeah, it's going to be timing out of the session and the drafts handler returns the session timeout error.
I personally excluded session timeout from draft saving in Wedge, for this very reason.
This is most probably something related to session verification. I suspect that this bug might also appear at other actions.
Not the way it's happening here.
Started typing now (2013/11/30 @ 14:17 ECT).
I'll post it later when I come back home. :P
ETA: it's now midnight, so about 8 hours after not even a session error... ???
I'd say this has been probably fixed in the meantime whatever it was.