Xbox Live is currently down for some users attempting to sign into their accounts on an Xbox 360 console, Zune PC client, Windows 8 or Windows Phone and more, according to the Xbox Live service status page.
"It looks like you've been disconnected from Xbox Live and worse, you can't sign back in!" reads the latest update, posted at 9:16 p.m. ET. "We will get this fixed as quickly as possible. Thanks for being patient while we sort this out."
Today also marks the release of Call of Duty: Black Ops 2's latest downloadable content, Revolution. Affected players will have to wait for service to return before being able to access their accounts.
Update: As of 9 p.m. ET, Jan. 29, Xbox Live is up and running, according to its support website.