Game unplayable after 1.6.1 update.

When playing without the launcher, on version 1.5.2, I get 50+ fps. When playing with the launcher on 1.5.2 or 1.6.1, I drop to 1-3 fps. My java is at the newest version. The lag intensifies when walking, often dropping to 0 fps. All minecraft settings are at the minimum levels, such as smooth lighting being off. I have never had much fps trouble before, and I can't figure out what to do.