Flex module error

I'm trying to load a module into a flex 4 application (the module was compiled using SDK4 as well) but I got this error (I'm migrating this app from Flex 3 to Flex 4):

VerifyError: Error #1014: Class mx.core::LayoutContainer coul开发者_C百科d not be found.

at flash.display::MovieClip/nextFrame()
at mx.core::FlexModuleFactory/deferredNextFrame()
at mx.core::FlexModuleFactory/update()
at mx.core::FlexModuleFactory/moduleCompleteHandler()

ReferenceError: Error #1065: Variable Step3_img_logo is not defined.

at flash.display::MovieClip/nextFrame()
at mx.core::FlexModuleFactory/deferredNextFrame()
at mx.core::FlexModuleFactory/update()
at mx.core::FlexModuleFactory/moduleCompleteHandler()

I'm using this code to add the module to a VBox:

var module:ModuleLoader = new ModuleLoader(); module.url = "layout/ImportContacts.swf?id_user=45"; moduleContainer.addChild(module);

Any ideas?

is your module compiled as Spark or Halo instance?

Did you load all RSLs you need?

problem was I created the module in a different project and it was optimized for it. tks.