Blackberry reveals failure cause

The maker of the Blackberry wireless e-mail device says an insufficiently tested software upgrade was the cause of this week's network failure.
Blackberry's US and North American users lost their service on Tuesday and Wednesday as a result of the problem.

Research In Motion (RIM) said it was now looking to improve its testing and recovery processes to prevent such an outage happening again.

There are about eight million Blackberry users around the world.

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