Minecraft freezes at mojang logo

When i try to load up the game it freezes on the mojang screen and after about 10 min the game starts up. i can than play it at around 20fps but it will drop from time to time to 5,3,0 fps over and over again.When i try to open chest, craftingtables, furnes, ext... the game freezes for 10 sec also when i start up the game the news bar won't load up. i have had this problem 2 times now since the update 1.5.2, i hope that this is a fixeble bug
Alse note--> I have already updated my java and graphics card+reinstaled my minecraft, force updated it. i play minecraft since the beta 1.7.1 or 2 and have never had that problem before.
pleas help me