Yes, this looks very familiar to me, although I thought the problem only occurs
if I both sign and encrypt the message.
I can't remember GpgOL's S/MIME support setting; and I'm unable to verify,
because I uninstalled it in the meantime (switched from OpenPGP to S/MIME
solution). You can mark #1130 a duplicate of #1137 if you like (though mine was
created 10 days earlier).

Nope, I'm using MS Outlook 2003 and #1110 crashes in Outlook 2007, whereas his
Outlook 2003 seems to work fine for him.
BTW: My Outlook 2003 doesn't crash, it just shows garbled content in the message
body (but that may be by luck).