Users across the globe have taken to Twitter to report problems with the instant messaging service, prompting a response from Google on its Apps status page.
"We're investigating reports of an issue with Google Talk," the company said at 11.50am UK time. "We will provide more information shortly."
Ten minutes later, it added: "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 behaviour."
After several updates explaining that the problem was still being investigated, some service was restored by around 3.20pm
"Google Talk service has already been restored for some users, and we expect a resolution for all users in the near future." the company said at 3.50pm.
"Please note this time frame is an estimate and may change."