updated 10:41 am EST, Thu February 28, 2013
Glitches ongoing since early Thursday
(Updated with service restoration info) Several iCloud services are being affected by "problems," Apple's system status page confirms. The errors began around 4AM Eastern time on Thursday, and have persisted since then. Photo Stream, backup, and Documents in the Cloud are being affected; Apple isn't saying what the exact problems are, but does claim that less than 3 percent of users have been impacted.
A previous round of errors hit Apple's online services just one week ago. Then, though, the company's app stores fell prey, along with iCloud calendars.
Update: Apple indicates that all services have been restored as of shortly before 3PM Eastern.