The microblogging service went down on Thursday with millions of users unable to access their accounts.
Users across Europe and the United States are reporting that they cannot log on to their Twitter accounts.
Twitter announced on its status page that "users may be experiencing issues accessing Twitter."
The social network has not announced yet what is causing the problems but assures Twitters that their engineers are "currently working to resolve the issue."
Twitter also experienced technical problems just last month, when its service was down for two hours due to a "cascading bug."
Mazen Rawashdeh, VP of Engineering at Twitter had said the issue last month was a cascading bug in one of their infrastructure components.
"A cascading bug is a bug with an effect that isn’t confined to a particular software element, rather its effect "cascades" into other elements as well," says Rawashdeh on the site’s blog.
"One of the characterics of such a bug is that it can have a significant impact on all users, worldwide, which was the case today. As soon as we discovered it we took corrective actions, which included rolling back to a previous stable version of Twitter."
Twitter says they have had at least 99.96% site reliability and stability in the past six months.
Twitter is not the only social service to experience difficulties today. Google Talk was down for several hours today before being resolved.