LibGDX Box2D physics app crash at launch

Question

I'm using a Win 7 64-bit system. LibGDX gdx-helloworld-android app works fine. It doesn't have any box2D stuff. But when I try to use run a physics demo/test, for example those found at http://code.google.com/p/libgdx/source/browse/trunk/tests/gdx-tests/src/com/badlogic/gdx/tests/box2d/ the app crashes on launch. Same thing happened with AndEngine physics examples too. So is the JNI box2D stuff processor dependent? Should I re-build the Box2D libraries using the android NDK and Cygwin as mentioned here: http://mayaposch.wordpress.com/2011/09/05/basic-andengine-and-box2d-extension-project/ so that the libraries work for my sytem config? Also, what are the folders armeabi and armeabi-v7a for? Are both the folders essential?