So far, this has only happened while out of game, in the main chat (any chat window, be it to a channel, a player, or typing in to the search friend bar or custom channel bar).
It's directly related to the key "W".
There's this weird time that I can't replicate on purpose (though I just successfully did it once right now) where it's as if the command key is held down. Thus, if I type "o", the friends list opens up, and if I type "o" again, it closes (as if I were holding down command and pressing "o"). Mashing the keyboard usually fixes this issues (I believe just hitting the command key).
However, when it's in this state, and you type "w" in to a chat (or a search), instead of closing that window, it will crash Starcraft.
If anyone can help me find a solid way to replicate the phantom-command-held-down situation, much appreciated! I'm almost 100% positive that it has something to do with command-m (making it windowed, then back to fullscreen).
I'll update this later today, if I figure more out.