Update: All services have been restored as of 4:41 PST.
A number of AppleInsider readers reported on Sunday that they could not send or receive iMessages from their iPhones and iPads, a problem that is becoming more common since the company's newest iOS 6 was released in September.
According to Apple's iCloud system status webpage, "some" users unable to use iMessage or place FaceTime calls, with the error coming less than two days after an issue appeared with iCloud storage upgrade payment transactions. Apple said service will return to normal "ASAP."
Sunday's downtime marks the fourth such outage in the past three months, with one incident in September and two in October (1, 2) affecting users of iMessage on both iOS and OS X clients. At the time, messages sent through Apple's proprietary service were pushed through as SMS texts.
While iMessage and FaceTime appear to be the most prone to errors, iCloud's email service has also seen problems, the latest being a September outage that affected 1.1 percent of all users.
Introduced alongside iOS 5, iMessage is Apple's smartphone-integrated answer to online messaging services like AOL Instant Messenger and Google Chat. The service is data based, allowing iOS device users to communicate with each other and Macs running OS X 10.8 Mountain Lion, without racking up text fees.