A huge fps drop

Whenever i log into to play mine craft in the recent snapshots leading up to 1.6 i experience a major fps drop the newest one i didn't drop as fast but it was pretty quick i go from about 175 fps to 15 in only about 3 seconds. There is lot more lag.Even when i switch my settings down that dosent help it performs just as well as max settings which is really bad. I mean 175 is what i usually play at on regular mine craft at max settings so i dont think it should be 15 . I also noticed that it seems to frag alot of files i defraged minecraft with a program known as razer game booster it took 15 minutes and had over 15,000 fragged files or something like that which is alot and i mean alot it might be due to an memory leak. But just thought you should know