Edit: After half day, my wife’s Mac started having the same problem. I have then applied the solution that I found in the Apple
References Found To Suggest Siri Diction Maybe Coming To iPods and iPads In iOS 5.1 beta –
We seen iOS 5.1 beta announced yesterday and the code diggers got down to work. 9to5Mac discovered the reference shown in the picture suggests that Apple maybe thinking about releasing Siri Dictation for iPad. The Dictation setting is not found in the same place as the iPhone 4s but a new place under Keyboard this could suggest that this is something we can expect to see released from Apple in the future. Cult Of Mac also discovered the same style of reference in the iOS 5.1 beta 3 for iPod Touch.
The found text explains the iOS dictations privacy details which was not available to view on older versions of the iOS. Siri Dictation is currently only a iPhone 4s Service.