LiveJournal uses multiple providers to determine how to route traffic from the Internet to our data center. One of those providers went down, which meant anyone who was being routed through this provider couldn't reach LiveJournal. We've temporarily stopped routing any traffic through this provider until they've fixed the problem. Whenever things are back to normal on their end, we'll start routing traffic through them again.
We don't expect there to be any further accessibility issues from this, but if you find yourself unable to reach the site over the next few hours, please send an email to email@example.com and let us know.