Thanks a lot; I was thinking of something else (a comet, maybe?) affecting the Earth's orbit, and sending the planet out of it...
If an object massive enough to impart that much energy hit the Earth, the impact would be a major problem. If something massive enough to pull the Earth off course without actually touching it flew by, I still think there would be a lot of damage from the gravity gradient, but I suppose it's possible. It seems unlikely for a massive enough object to come so close with all the space around that isn't that close to the Earth.