If you have downloaded android 4.0, you should read the article.
$ANDROID_ROOT/tools/android.bat is changed when you download android 4.0, and it is not compatible with previous versions.
So you should do some work.
1. You should use ndk-r7 to build native codes
Because android.bat of android 4.0 doesn't generate default.properties, it generates project.properties.
NDK versions before ndk-r7 don't recognize project.properties.
2. You should modify cocos2dx/Android.mk manually before compilation
Please refer Build project with ndk-r7.
3. You should use create-android-project.bat or create-android-project.sh to generate new android project¶
Because android.bat of android 4.0 doesn't generate res/drawable-hdpi, res/drawable-ldpi and res/drawable-mdpi.
New version(cocos2d-1.0.1-x-0.10.0) of create-android-project.bat or create-android-project.sh copy these folders from HelloWorld.
OK, good luck for you.