Microsoft is still working to restore its Instant Messenger service after three days of problems.
The company says about a third of its customers worldwide are experiencing service interruptions.
A Microsoft spokeswoman said engineers are still working on the problem and are unable to say when it will be resolved.
The spokeswoman said: "At the moment we are still working on it. It's a hardware issue and engineers can't give a specific time of when it will be resolved."
Microsoft Vice President Rich Bray has apologised to customers for the interruptions.
He said: "An extremely rare set of circumstances occurred when one of our database servers had a disk controller fail.
"The backup for this controller also had an error, which resulted in a more lengthy path to recovery. We are working as quickly as possible to restore service to all MSN Messenger customers."
He assured users their buddy contact lists have not been lost.
PA