Unable to instantiate activity

I received following error on the google play store and have no idea why it happens?
Does someone have any idea? is this a unity bug?

It happend on a phone with Android 4.4 (Galaxy Note II (t03g))

java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.mycompany.myappname/com.unity3d.player.UnityPlayerNativeActivity}: java.lang.ClassNotFoundException: Didn't find class "com.unity3d.player.UnityPlayerNativeActivity" on path: DexPathList[[zip file "/mnt/asec/com.mycompany.myappname-1/pkg.apk"],nativeLibraryDirectories=[/vendor/lib, /system/lib]]
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2306)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2471)
at android.app.ActivityThread.access$900(ActivityThread.java:175)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1308)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:146)
at android.app.ActivityThread.main(ActivityThread.java:5602)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.ClassNotFoundException: Didn't find class "com.unity3d.player.UnityPlayerNativeActivity" on path: DexPathList[[zip file "/mnt/asec/com.mycompany.myappname-1/pkg.apk"],nativeLibraryDirectories=[/vendor/lib, /system/lib]]
at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:67)
at java.lang.ClassLoader.loadClass(ClassLoader.java:497)
at java.lang.ClassLoader.loadClass(ClassLoader.java:457)
at android.app.Instrumentation.newActivity(Instrumentation.java:1067)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2297)
... 11 more
Suppressed: java.io.IOException: unable to open DEX file
at dalvik.system.DexFile.openDexFileNative(Native Method)
at dalvik.system.DexFile.openDexFile(DexFile.java:309)
at dalvik.system.DexFile.<init>(DexFile.java:82)
at dalvik.system.DexFile.<init>(DexFile.java:61)
at dalvik.system.DexPathList.loadDexFile(DexPathList.java:263)
at dalvik.system.DexPathList.makeDexElements(DexPathList.java:230)
at dalvik.system.DexPathList.<init>(DexPathList.java:112)
at dalvik.system.BaseDexClassLoader.<init>(BaseDexClassLoader.java:58)
at dalvik.system.PathClassLoader.<init>(PathClassLoader.java:65)
at android.app.ApplicationLoaders.getClassLoader(ApplicationLoaders.java:57)
at android.app.LoadedApk.getClassLoader(LoadedApk.java:326)
at android.app.LoadedApk.makeApplication(LoadedApk.java:508)
at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4703)
at android.app.ActivityThread.access$1600(ActivityThread.java:175)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1368)
... 8 more