Android download error "package not signed correctly

I have signed and published my game app on the Android Developer Console. I'm using Unity 3.2 on Windows 7. My users are unable to download and install my game. They are receiving an error message while the app is about 80-95% downloaded. It spits an error message "package not signed correctly". I've published several "NEW" test applications and I know the apk is signed correctly. To test this, I carefully created a "NEW" keystore in Unity. Changed the name of the package and I am still receiving the same error. I'm doing something else wrong? Does anybody have any ideas?

Please look at my manifest. Is this a possible problem.? Have I not created the correct licensing code? Am I missing something in the script or is it something entirely different like the JDK or SDK downloads? I need someone to troubleshoot this with me.

thanx

 <?xml version="1.0" encoding="utf-8"?>
 <manifest
     xmlns:android="http://schemas.android.com/apk/res/android"
     package="com.unity3d.player"
     android:installLocation="preferExternal"
     android:versionCode="2"
     android:versionName="1.1">
     <supports-screens
         android:smallScreens="true"
         android:normalScreens="true"
         android:largeScreens="true"
         android:xlargeScreens="true"
         android:anyDensity="true"/>
     <uses-sdk android:minSdkVersion="7" />
     
     <application
         android:icon="@drawable/app_icon"
         android:label="@string/app_name"
         android:debuggable="false">
         <activity android:name="com.unity3d.player.UnityPlayerActivity"
                   android:label="@string/app_name"
                   android:configChanges="keyboard|keyboardHidden|orientation">
                 <intent-filter>
                     <action android:name="android.intent.action.MAIN" />
                     <category android:name="android.intent.category.LAUNCHER" />
                 </intent-filter>
         </activity>
         <activity android:name="com.unity3d.player.VideoPlayer"
                   android:label="@string/app_name"
                   android:configChanges="keyboard|keyboardHidden|orientation">
         </activity>
 
 
             <!-- ACTIVITIES -->
         <activity android:name="com.prime31.EtceteraProxyActivity"></activity>
         <activity android:name="com.prime31.WebViewActivity" android:configChanges="orientation"></activity>
         <activity android:name="com.prime31.P31VideoPlayerActivity" android:configChanges="keyboard|keyboardHidden|orientation"></activity>
 
             <!-- META-DATA -->
 
         </application>
 
         <!-- PERMISSIONS -->
 </manifest>