Make sure that you don't have too many apps running in the background. Also keep an eye on your free memory. Do this by options>status>file free. To properly close your apps you must use the menu key and select close or exit. To many apps running and/or too little memory will cause your phone to reboot.
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Have you recently saved a picture to your Media card, or do you have BBM 5 set to save pictures from a Group to your card?
The problem sounds like a corrupted file on your card. Remove it from the device, le� it reboot, and see if that stops the problem. If it does, transfer the files to your computer, and reformat your media card.
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