Twitter was also offline in some areas, and Microsoft's Azure cloud service was out across Europe.
Google first reported problems with Google Talk early Thursday through an update to its Apps dashboard. "We're investigating reports of an issue with Google Talk," Google said at 6:40 a.m. Eastern.
"We're aware of a problem with Google Talk affecting a majority of users. The affected users are able to access Google Talk, but are seeing error messages and/or other unexpected behavior," the company said at 6:50 a.m.
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Google continued to report problems with the service throughout the morning. At 10:50 a.m., it said the problem was partly under control. "Google Talk service has already been restored for some users, and we expect a resolution for all users in the near future."
At 11:25 a.m., Google said it had fixed the problems and the service had been fully restored. "We apologize for the inconvenience and thank you for your patience and continued support. Please rest assured that system reliability is a top priority at Google, and we are making continuous improvements to make our systems better."
The search giant did not offer an explanation for the interruption. The company's other online services, including Gmail and Google Groups, did not appear to have been affected.
Twitter was also down for parts of Thursday. "Howdy folks, looks like we're experiencing a small interruption of Twitter.com and some mobile clients. Thanks for your patience!" the company tweeted. Service appeared to have been fully restored by midday.
In what was one of the toughest days in the relatively brief history of the cloud, Microsoft's Windows Azure was also out.
"We are experiencing an availability issue in the West Europe sub-region, which impacts access to hosted services in this region. We are actively investigating this issue and working to resolve it as soon as possible," Microsoft said on its Azure dashboard.
"Further updates will be published to keep you apprised of the situation. We apologize for any inconvenience this causes our customers," the company said.
Microsoft did not state the cause of the outage.
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