Flash Builder Beta 2

Adobe... who's stupid idea was it to force users to "upgrade" to Beta 2?

If you've been getting this error trying to load a style SWF:
VerifyError: Error #1014: Class mx.modules::ModuleBase could not be found.

at flash.display::MovieClip/nextFrame()
at mx.core::FlexModuleFactory/deferredNextFrame()[E:\dev\gumbo_beta2\frameworks\projects\framework\src\mx\core\FlexModuleFactory.as:574]
at mx.core::FlexModuleFactory/update()[E:\dev\gumbo_beta2\frameworks\projects\framework\src\mx\core\FlexModuleFactory.as:402]
at mx.core::FlexModuleFactory/moduleCompleteHandler()[E:\dev\gumbo_beta2\frameworks\projects\framework\src\mx\core\FlexModuleFactory.as:652]

1] right click the project that contains the CSS file your compiling
2] goto Flex Build Path
3] Change framework linkage to merged
4] Click on the Flex 4.0.0 build path and Remove it
5] Click Add Flex SDK to readd it
6] Click ok to exit and re-clean your project

Hopefully this will fix your compiler bug.