All online services provided by BlackBerry’s Canadian maker Research In Motion have now been wiped out for a third day in four continents, just two days before rival Apple's new iPhone 4S goes on sale.
RIM advised clients of an outage in the Americas and said it was working to restore services as customers worldwide continued to suffer patchy email and no access to browsing and messaging.
RIM, which had said on Tuesday services had returned to normal, said later it was still working to resolve the problem.
"The messaging and browsing delays ... were caused by a core switch failure within RIM's infrastructure," it said. "As a result, a large backlog of data was generated and we are now working to clear that backlog and restore normal service."
RIM did not say how long it might take. In India, top mobile carrier Bharti Airtel sent text messages to customers saying BlackBerry services were likely to be restored in four to five hours.
The service disruptions are the worst since an outage swept north America two years ago, and come as Apple prepares to put on sale its already sold-out iPhone 4S on Friday.
"It's a blow upon a bruise. It comes at a bad time," said Richard Windsor, global technology specialist at Nomura.
"One possibility could be that it encourages client companies to look more at other options such as allowing users to connect their own devices to the corporate server and save themselves the cost of buying everyone a BlackBerry."