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What caused the worldwide Blackberry crash?

12 October 2011 Last updated at 15:13 BST

It has been another frustrating day for the millions of Blackberry customers across the world who are unable to access the likes of BBM, email and the internet.

Users have taken to social-networking sites such as Twitter to vent their frustration.

Rory Cellan-Jones looks at what has caused the meltdown.