At 11:45 a.m. EDT reports began to circulate of users unable to access either Twitter's main site or the Twitter's Blogger site, ZDNet.com reported.
Around noon, Twitter managed to come online long enough to report: "Users may be experiencing issues accessing Twitter. Our engineers are currently working to resolve the issue."
Twitter's outage followed one suffered by Google Talk at about 6:40 a.m. EDT that knocked Talk and its related Voice-over-Internet Protocol and video-conferencing services offline.
Google was reporting a restoration of its services by 1 p.m.
There was some speculation the outages for Google and Twitter could have been because of London Olympic Internet traffic load or broad Distributed Denial of Service attacks, but experts said there was no concrete evidence for either.
In June Twitter went down because of a "cascaded bug in one of our infrastructure components" during a software update that went wrong, the company said.