Changes are on SVN. Thanks everyone, that's great!
I made one more shotgun change on the suspicion the entire window destroy event was fired twice - it's one of those things that shouldn't be possible, but it seems like that's what really fixed it! I guess some OpenGL drivers have some bug (or just work that way, I don't know) where the window got destroyed twice for some reason. Really weird. Well, it's fixed!
will push out 28.4 asap!