Problems after overlaying AIR SDK on Flex SDK

问题:

I'm trying to overlay AIR SDK on Flex SDK on Windows machine but I am encountering issues afterwards. I tried overlaying with several official versions of both SDKs (including Apache Flex SDK) and followed the steps mentioned here: http://helpx.adobe.com/x-productkb/multi/how-overlay-air-sdk-flex-sdk.html

However, after pasting the AIR SDK contents in the Flex SDK folder and overwriting existing files FlashBuilder reports the following Errors when I change projects SDK:

"Could not resolve <mx:ViewStack> to a component implementation."
"Could not resolve <s:SWFLoader> to a component implementation."

I made sure that the namespace version in application descriptor is stated correctly.

What am I missing to successfully overlay both SDKs?