My apps will not install on device when downloaded from the Android Market

I am unable to install my app onto a device even when it is downloaded from the Android Market. How can this be possible? If it were signed incorrectly wouldn't the market not accept it? I have tried to install it by isolating various activities but none seem to work even when I reduce it to a simple hello world application. The app has a tab view, two being webviews [one includes a reload button] and one tab that allows a user to send an email to a submiss开发者_StackOverflow社区ion page. Does anyone have any ideas as to what I am missing?

Thank you all very much in advance.

EDIT:

It's being downloaded on the LG Ally running 2.2.2 and my app runs fine on an 2.2 emulator. It is compiled with a min level of 4. Here is my AndroidManifest file

<?xml version="1.0" encoding="utf-8"?>

<application android:icon="@drawable/icon" android:label="@string/app_name" android:debuggable="false">
    <activity android:name=".BrotipsTabs"
              android:label="Brotips">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
        </activity>
    <activity android:name=".TabWidget"
          android:label="@string/app_name" 
          android:theme="@android:style/Theme.NoTitleBar">
</activity>

<activity android:name=".Random"
          android:label="@string/app_name" 
          android:theme="@android:style/Theme.NoTitleBar">
</activity>

<activity android:name=".Sub"
          android:label="@string/app_name" 
          android:theme="@android:style/Theme.NoTitleBar">
</activity>
<activity android:name=".BrotipsTabs" android:label="@string/app_name"
      android:theme="@android:style/Theme.NoTitleBar">
      </activity>
<meta-data android:name="com.mobclix.APPLICATION_ID" android:value="<Key>"/>
<activity android:name="com.mobclix.android.sdk.MobclixBrowserActivity" android:theme="@android:style/Theme.Translucent.NoTitleBar"/>
</application>
    <uses-permission android:name="android.permission.INTERNET" /> <uses-permission android:name="android.permission.READ_PHONE_STATE" /> <uses-permission
android:name="android.permission.ACCESS_NETWORK_STATE" />
</manifest>

By not working I mean it refuses to install and claims it never did while an icon remains on the phone.

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Do you have any previous versions of your app installed on your phone? If you have an apk that is signed with the debug signature (which eclipse uses when you push run) and try to install it from the market which is signed with an actual signature then it will fail due to the two signatures being different. The message that it shows you is different on different devices I've found. If you have any previous versions of your app installed you should uninstall them and try to install from the market again. You should be good to go.