06-11-2013 11:29 AM
Welcome to BlackBerry Support Forums
There are many reasons for the problem you're having ! You should check your available device memory , Check for any 3rd party app which may be the reason, shouldn't allow any apps to run in the background and many other factors , a little explanation will help to assist you .
Meanwhile please check this Knowledge Base :
KB14320 How to maximize battery life and free memory on the BlackBerry smartphone