Skype, the online telephone service, said Friday that it was "on the road to recovery" after a software glitch prevented most of its 220 million-plus subscribers from signing on to the network.

In a statement posted on its Web site at 11:00 GMT Friday, Skype said its service was "stabilizing" but added "we know we're not out of the woods yet."

Skype officials blamed Thursday's outage on a "deficiency in an algorithm" within the networking software that controls the interaction between the user's Skype client and the rest of the Skype network.

This deficiency kept subscribers from logging on to the Skype network, forcing engineers to work throughout the day and night to bring the service back online. While Skype said it doesn't know what caused the glitch to suddenly disrupt service, it was able to dispel a couple of rumors swirling throughout the blogosphere.

"Neither Wednesday's planned maintenance of our Web-based payment services nor any form of attack was related to the current sign-on issues in any way," according to its Web site.

The outage also prevented new users from downloading the Skype software.

Using a peer-to-peer infrastructure, Skype allows subscribers to make telephone calls to other subscribers for free over their computers. Calls are routed through other users' computers instead of a central hub. The offending software bug is thought to disrupt the flow of data from user computers to Skype servers located around the world.

Until Thursday, Skype had avoided any major outages while competitors such as Comcast, BT Group and Teleblend all have endured outages of varying degrees in the past year.

Based in Luxembourg, Skype was acquired by online auctioneer eBay in 2005 for more than $2.5 billion.