Taken from click here
It generally occurs when the send option "Upload Larger Images to the Web When Sending a Photo E-mail" is *un-checked*, but it does not usually manifest until a new compose window, or a saved draft has been opened.
This option is available only when you are signed in, but if it is un-checked it still causes the shutdown bug even when not signed in.
So make sure the option "Upload Larger Images to the Web When Sending a Photo E-mail" is *checked* at: Tools->Options->Send [tab] (available only when signed into Windows Live through WLMail).
However, if you do find that "Upload Larger Images to the Web When Sending a Photo E-mail" is actually checked (which it is by default), then just uncheck it and click "Apply", then check it again and click "Apply" again. Some have had to do that to fix their WLMail shut down bug that was occurring despite that option having never been unchecked.