ClassNotFoundException

java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.droidacid.apticalc/com.droidacid.apticalc.MainMenu}: java.lang.ClassNotFoundException: com.droidacid.apticalc.MainMenu in loader dalvik.system.PathClassLoader[/mnt/asec/com.droidacid.apticalc-1/pkg.apk]
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1653)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1755)
at android.app.ActivityThread.access$1600(ActivityThread.java:156)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1001)
at android.os.Handler.dispatchMessage(Handler.java:130)
at android.os.Looper.loop(SourceFile:351)
at android.app.ActivityThread.main(ActivityThread.java:3822)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:538)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:969)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:727)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.ClassNotFoundException: com.droidacid.apticalc.MainMenu in loader dalvik.system.PathClassLoader[/mnt/asec/com.droidacid.apticalc-1/pkg.apk]
at dalvik.system.PathClassLoader.findClass(PathClassLoader.java:271)
at java.lang.ClassLoader.loadClass(ClassLoader.java:582)
at java.lang.ClassLoader.loadClass(ClassLoader.java:542)
at android.app.Instrumentation.newActivity(Instrumentation.java:1056)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1645)
... 11 more