Certainly the most important event in the tech world in the past few days was the unavailability of the VoIP client Skype. Without any notice the service had stopped working on Thursday and it was restored on Friday night, although for some users it was unavailable until Sunday.

As you can imagine, the speculations went rampant and the conspiracy theories included a possible DoS attack, a problem with the Skype’s infrastructure, a programmed maintenance period that went wrong and even an alleged bug in the software itself. 

But Skype’s officials denied all the rumors and today they posted an explanation on Heartbeat Skype, the company’s official blog, as promised yesterday.

“The disruption was initiated by a massive restart of our user’s computers across the globe within a very short timeframe as they re-booted after receiving a routine software update. The abnormally high number of restarts affected Skype’s network resources. This caused a flood of log-in requests, which, combined with the lack of peer-to-peer network resources, prompted a chain reaction that had a critical impact.” explains Villu Arak, a Skype spokesman.

As you can see it was just a coincidence of events, but as Arak pointed out a bug was also involved.

“Normally Skype’s peer-to-peer network has an inbuilt ability to self-heal, however, this event revealed a previously unseen software bug within the network resource allocation algorithm which prevented the self-healing function from working quickly.” he said.

It seems like Skype has learned the lesson and according to Arrak’s post the company has already taken some measures to prevent this type of incidents in the future.

“Skype has now identified and already introduced a number of improvements to its software to ensure that our users will not be similarly affected in the unlikely possibility of this combination of events recurring.” Arak said.

Skype, which was acquired by the auction site eBay, was founded by Niklas Zennstrom and Janus Friis, who are also the founders of video site Joost. The program, which uses peer-to-peer technology to connect phone calls, instant messages and videos between its users, became an instant hit after its launch in August 2003.

Skype experienced some connectivity problems in 2005, when the service was down for a few hours, but after that no other major disrupting event was reported.