The service outages suffered by BlackBerry users in the last two days were caused by a network switch failure, followed by a malfunction in the system that is supposed to direct traffic to a redundant switch in the event of such a failure.

"The messaging and browsing delays being experienced by BlackBerry users in Europe, the Middle East, Africa, India, Brazil, Chile and Argentina were caused by a core switch failure within RIM’s infrastructure," the company said in a statement. "Although the system is designed to failover to a back-up switch, the failover did not function as previously tested."

"As a result, a large backlog of data was generated and we are now working to clear that backlog and restore normal service as quickly as possible."

There are many reasons why the initial switch may have malfunctioned, Ovum analyst Nick Dillon said this morning.

"When RIM suffered outages in the past, it was often caused by a software-related issue, or it could just be a hardware failure," he said. "It could have been a problem with the power supply, but then we probably wouldn’t have had these recurring issues."

The failover issue might have been averted with more redundancy, Dillon said, but he added that RIM has generally improved the availability of its services in the last couple few years. "Before 2008, they suffered outages on a regular basis, but since they’ve had fewer since them," he said. "I’d argue that they have handled their infrastructure quite well."

Furthermore, the fact that RIM offers an integrated device and data service means that outages are particularly conspicuous. "One of their key competitive strengths is that they offer a vertically integrated service," he explained. "The downside of that is that its pretty obvious when something goes wrong."

Dillon believes the outages will have some impact on RIM’s already troubled business. "I would imagine there will be some customers who, as a result of these events, who might think more carefully about buying BlackBerrys."

Last month, RIM reported a 15% drop in revenue for the most recent financial quarter, down to $4.2 billion. This was due “to the lower number of BlackBerry handheld devices and PlayBook [tablets] shipped”, said chief financial officer Brian Bidulka at the time.