Millions of BlackBerry users have entered their third day of an internet blackout, with no word on when services might be restored.
RIM, the Canadian company behind the BlackBerry brand, released limited details of the source of the ongoing problems last night.
"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," it said in a statement at 10PM.
"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.
"We apologize for any inconvenience and we will continue to keep you informed."
It was not immediately clear however if the broken switch - which in the context of internet infrastructure refers to an expensive and specialised piece of equipment that routes traffic in a data centre - was the original cause of the blackout on Monday or a secondary problem.
This morning a RIM spokesman said the switch was still the source of the ongoing problems.
BlackBerry are now enduring their third working day without mobile internet access, including email and RIM's instant messenger, BBM. Services were briefly restored on Tuesday morning, but collapsed again within three hours.
Lord Sugar told his Twitter followers the outage appeared unprecedented.
"In all my years in IT biz, I have never seen such a outage as experienced by Blackberry. I can't understand why it's taking so long to fix," he said.
"All my companies use [BlackBerries], every one so reliant on getting email on the move, people don't know if they are coming or going."
Criticism of RIM's communication strategy continued, with experts lined up to condemn its public handling of the crisis. Alastair Campbell, Tony Blair's former communications chief, offered the firm some "free advice" this morning.
"Explain while you fix. Apologise when you have. Recompense after. Handling so far woeful," he said.
The timing is particularly unfortunate for RIM, according to industry analysts, as Apple launches the iPhone 4S and competing internet services this week, including iMessage, a rival to BBM.
Ian Fogg, a mobile industry analyst at Forrester, said RIM had built its reputation on reliability.
"RIM is in danger of becoming its own worst enemy if it is unable to reliably operate the communication services that have differentiated it," he said on his blog.
"BBM is the reason many young consumers stay with BlackBerry. If it doesn’t work, they will leave RIM."