01-31-2013 12:45 AM
Welcome to BlackBerry Support Forums
Many reasons for a device to freeze like if you install an unknown third party application, low memory , applications running in the background or sometimes because of device OS itself.
Try to start your device on Safe Mode and notice if your device freezes , if not then remove or delete any third party application one by one to know which application is responsible for the issue.
KB17877 : How to start a BlackBerry smartphone in Safe Mode
Or the easiest way is first do a backup of your device using Desktop Software , then perform a Clean OS Reload , after reload don't restore any application from the backup , restore only your contacts or calender entries, If problem disappear then install one application at a time , if after installing any appliction issue appears just delete that particluar application,
KB11320 : How to perform a clean reload of the BlackBerry Device software using BlackBerry desktop software for windows