A problem with my Minecraft

Over the last few weeks, i have been experiencing very annoying problems with my minecraft, i have tryed to reinstall another .minecraft but no luck!


Basically, Every time am on a world and am on peaceful mode and want to be on normal or higher, as soon as i change it and exit the options screen, the world then stops and the 'Saving Chunks' screen appears, this stays for about 1 minuite to then show a glimpse of the 'Minecraft has Crashed' Screen just before the screen goes black and i have to exit it and have to start up the launcher up again.


It woulden't be as bad if it took me o the hompage but for minecraft to crash and me have to start it up again (whitch takes quite a while on my currant old computer)





If anyone has any thing to say on how to fix it or what it is that has happened, Please let me know!