When i normally played minecraft about 2 weeks ago i got 100+ fps but i went on vacation then when i got back i went to play minecraft and i got 20-30 fps. WTF! Can someone tell me why minecraft all of a sudden did not work. BTW: it started b4 1.6.1 came out so it was all the same version.
This is incredibly possible.
If you can't get it to work, try installing Optifine