A bug with iOS 6.1 is causing havoc in enterprise environments. Released a couple weeks ago, a new bug was introduced with iOS 6.1 causes excessive server load when responding certain recurring calendar events on a Microsoft Exchange account. The bug specifically deals with a modification of a single appointment from a repeating event.
When you respond to an exception to a recurring calendar event with a Microsoft Exchange account on a device running iOS 6.1, the device may begin to generate excessive communication with Microsoft Exchange Server. You may notice increased network activity or reduced battery life on the iOS device. This extra network activity will be shown in the logs on Exchange Server and it may lead to the server blocking the iOS device. This can occur with iOS 6.1 and Microsoft Exchange 2010 SP1 or later, or Microsoft Exchange Online (Office365).
Apple says a fix will be available in an upcoming iOS update, but doesn't provide details of what that may occur. In the mean time, Apple suggests users can try turning the calendar sync off, wait, then turn it back on it to clear the problem.
Apple Support
