Unable to get xtify Provider (ClassNotFound exception)

Question

I've implemented the xtify sample in Android that I download from http://developer.xtify.com/display/sdk/Download+the+Xtify+SDKs and created an gcm application in console as described in getting started, but when I execute I get this error:

FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to get provider com.xtify.sdk.db.Provider:         java.lang.ClassNotFoundException: com.xtify.sdk.db.Provider in loader dalvik.system.PathClassLoader[/data/app/com.example.gcmessaging6-1.apk]
at android.app.ActivityThread.installProvider(ActivityThread.java:4515)
at android.app.ActivityThread.installContentProviders(ActivityThread.java:4287)
at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4243)
at android.app.ActivityThread.access$3000(ActivityThread.java:126)

I have the package name and the provider in the manifest file (and the permissions):

<manifest xmlns:android="http://schemas.android.com/apk/res/android"     package="com.xtify.samples.gcm"
        android:versionCode="3"
        android:versionName="3.0" 
        android:installLocation="internalOnly">
  <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="16" />

       <application
          android:icon="@drawable/ic_launcher"
          android:label="@string/app_name" >
         <provider
            android:name="com.xtify.sdk.db.Provider"
            android:authorities="com.xtify.samples.gcm.XTIFY_PROVIDER"
            android:exported="false" />
          .....
      </application>  

    </manifest>

The sdk is in the libs folder and added in build.

I've searched the problem but the solutions found don't work for me as I have the providers well configured as I saw. What can it be?

Regards, Alex