The outage began on Monday at around 4pm BST and left BlackBerry users including those in Europe, the Middle East, India and Africa without access to data services, including emails sent via the BlackBerry Enterprise Server (BES).
The explanation came via a hastily convened press conference on Thursday, in which Lazaridis (pictured) was joined by co-chief Jim Balsillie to explain the outages.
"On Monday, we had a hardware failure that caused a ripple effect in our system, a dual-redundant high-capacity core switch designed to protect the infrastructure failed, this caused a cascade failure in our system," Lazaridis said.
"There was a back-up switch but the back-up did not function as intended and this led to a backlog of data in the system. The failure in Europe, in turn, overloaded systems elsewhere. When we restarted the system based in Europe the data queue processing took much longer than we had expected to restore to our standard service levels, this backlog impaired service levels", he added.
During a question-and-answer session, the co-chiefs described the problems as "the largest outage we've ever experienced" and said that the cause of the failure was being investigated but that it could take some time to complete the root cause analysis because "systems like this don't fail this way. They're designed so they don't fail in this way", Lazaridis said.
The bosses also fielded questions about potential compensation for its users left without service but the chiefs said the company had focused its efforts on reinstating the network and had not yet discussed other issues.
The network is now back up and fully operational according to the company. It added that if users are still not receiving emails or are unable to use other data services, they may need to remove the battery and restart the handset in order to "regain synchronisation" on the devices.
Also on Thursday, ahead of the technical explanation, co-chief executive Mike Lazaridis issued a video apology to customers on YouTube.
"Since launching BlackBerry in 1999 it has been my goal to provide reliable real-time communications around the world. We did not deliver on that goal this week. Not even close," Lazaridis said.
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RIM is an extraordinary company with intelligent products — this is NOT the time to jump ship.
SilValgal by way of Waterloo