I get a cold sore every time my lips dry up and crack, (the virus lies dormant til it sees a chance of escape, I reckon) so in very cold, windy, or very hot weather, I have to slather on the lip salve. Some foods make my lips crack as well, especially salted nuts, so I only eat plain ones which I seem Ok with.
I don't think mouth ulcers are related, but they do tend to develop if you've got a cut or anything sore in your mouth ( I always get one if I've chomped the side of my cheek), so maybe the same cause.