User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.4) Gecko/2008102920 Firefox/3.0.4 Build Identifier: version 2.0.0.18 (20081105) I have seen this behavior several times on the most recent version (20081105) but have not been able to isolate the causes. I'll be composing a message that happens to contain UTF-8 characters (copy/pasted from another file). For no reason (i.e. I didn't click SEND or press Ctrl-Enter) TB Pops up the "Message contains UTF-8" warning as if I had tried to send the message. This has even happened while the focus was on a different window and the TB composition window was minimized. Reproducible: Couldn't Reproduce So far this has happened only when the message text contained UTF-8 characters, and it always pops up the warning dialog, giving me a chance to cancel out and continue composing. I have not seen an instance of TB actually sending a message before I told it to.

FYI: It doesn't try to send the message, it tries to store it as draft (autosave)

Which was fixed for Tb3 by just removing the pointless prompt.