Blackberry services are being restored after millions of customers were unable to access e-mail or send text messages following a power outage which began in Europe two days ago and spread across the globe to North America yesterday.
The messaging and browsing delays experienced by Blackberry users were caused by a core switch failure within RIM's infrastructure.
In a statement, Research in Motion (RIM), which makes Blackberry devices, said: "In Europe, Middle East, India and Africa, we are seeing a significant increase in service levels. Service levels are also progressing well in the US, Canada and Latin America, and we are seeing increased traffic throughput on most services, although there are still some delays and service levels may still vary.
"Our global teams are continuing to work as quickly as possible to restore full and consistent service across all regions."
RIM's UK managing director, Stephen Bates, told delegates at the company's annual Blackberry Innovation Forum in London: "We have 70 million customers worldwide, with seven million of those in the UK. Around 20 petabytes of data passes over our global infrastructure every month. We face complexity in troubleshooting the problems."
But the blackout may have damaged Blackberry's reputation among some users and accelerated the number of business customers already intending to switch to Apple's iPhone.
Many users took to Twitter to complain about the outage yesterday, including Lord Sugar who told his Twitter followers: "In all my years in IT biz, I have never seen such an outage as experienced by Blackberry. I can't understand why it's taking so long to fix."