Skype is trying to fix an outage that left its 220 million users unable to make cheap calls over the internet.
The company said this afternoon said that its service was stabilising but that it had not yet resolved the problem, which was apparently caused by a fault in its software that meant users could not sign on.
"We're on the road to recovery. Skype is stabilising, but this process may continue throughout the day - we're not out of the woods yet," a statement on Skype's website said.
Skype's chief security officer, Kurt Sauer, told the New York Times that what had happened was caused by "a unique set of events, the genesis of which is not entirely understood".
The flaw existed in every version of the Skype software that had been downloaded since 2003, engineers at the company said, but they were unsure as why the error, which had lain dormant for four years, had only affected the network now.
