Flex SDK 4.11 4.0 error after upgrading from 4.10 3.9

I have initially developed my flex applicaition in Flex SDK 4.6. I was able to upgrade my application to 4.10 3.9. But to support iOS 7 I am now using 4.11 sdk & air runtime 4.0. But unfortunately it is giving me this error:

Error #1065: Variable spark.skins::ActionScriptSkinBase is not defined. at global$init()[/Users/justinmclean/Documents/ApacheFlex4.11.0/frameworks/projects/mobiletheme/src/spark/skins/mobile/SkinnableContainerSkin.as:34] at Function/<anonymous>() at mx.styles::CSSStyleDeclaration/http://www.adobe.com/2006/flex/mx/internal::addDefaultStyleToProtoChain()[/Users/justinmclean/Documents/ApacheFlex4.11.0/frameworks/projects/framework/src/mx/styles/CSSStyleDeclaration.as:972] at mx.styles::CSSStyleDeclaration/http://www.adobe.com/2006/flex/mx/internal::addStyleToProtoChain()[/Users/justinmclean/Documents/ApacheFlex4.11.0/frameworks/projects/framework/src/mx/styles/CSSStyleDeclaration.as:899] at mx.styles::StyleProtoChain$/initProtoChain()[/Users/justinmclean/Documents/ApacheFlex4.11.0/frameworks/projects/framework/src/mx/styles/StyleProtoChain.as:258] at mx.core::UIComponent/http://www.adobe.com/2006/flex/mx/internal::initProtoChain()[/Users/justinmclean/Documents/ApacheFlex4.11.0/frameworks/projects/framework/src/mx/core/UIComponent.as:11189] at mx.core::UIComponent/regenerateStyleCache()[/Users/justinmclean/Documents/ApacheFlex4.11.0/frameworks/projects/framework/src/mx/core/UIComponent.as:11252] at mx.managers.systemClasses::ChildManager/addingChild()[/Users/justinmclean/Documents/ApacheFlex4.11.0/frameworks/projects/framework/src/mx/managers/systemClasses/ChildManager.as:168] at mx.managers.systemClasses::ChildManager/initializeTopLevelWindow()[/Users/justinmclean/Documents/ApacheFlex4.11.0/frameworks/projects/framework/src/mx/managers/systemClasses/ChildManager.as:360] at mx.managers::SystemManager/initializeTopLevelWindow()[/Users/justinmclean/Documents/ApacheFlex4.11.0/frameworks/projects/framework/src/mx/managers/SystemManager.as:3065] at mx.managers::SystemManager/http://www.adobe.com/2006/flex/mx/internal::kickOff()[/Users/justinmclean/Documents/ApacheFlex4.11.0/frameworks/projects/framework/src/mx/managers/SystemManager.as:2851] at mx.managers::SystemManager/http://www.adobe.com/2006/flex/mx/internal::preloader_completeHandler()[/Users/justinmclean/Documents/ApacheFlex4.11.0/frameworks/projects/framework/src/mx/managers/SystemManager.as:2731] at flash.events::EventDispatcher/dispatchEventFunction() at flash.events::EventDispatcher/dispatchEvent() at mx.preloaders::Preloader/timerHandler()[/Users/justinmclean/Documents/ApacheFlex4.11.0/frameworks/projects/framework/src/mx/preloaders/Preloader.as:572] at flash.utils::Timer/_timerDispatch() at flash.utils::Timer/tick()