Android清单文件活动错误

12-11 02:45:59.232: E/AndroidRuntime(348): FATAL EXCEPTION: main
12-11 02:45:59.232: E/AndroidRuntime(348): java.lang.RuntimeException: Unable to  instantiate activity ComponentInfo{com.ass.ui/com.ass.ui.Settings}: java.lang.InstantiationException: com.ass.ui.Settings
12-11 02:45:59.232: E/AndroidRuntime(348):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2585)
12-11 02:45:59.232: E/AndroidRuntime(348):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
12-11 02:45:59.232: E/AndroidRuntime(348):  at android.app.ActivityThread.access$2300(ActivityThread.java:125)
12-11 02:45:59.232: E/AndroidRuntime(348):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
12-11 02:45:59.232: E/AndroidRuntime(348):  at android.os.Handler.dispatchMessage(Handler.java:99)
12-11 02:45:59.232: E/AndroidRuntime(348):  at android.os.Looper.loop(Looper.java:123)
12-11 02:45:59.232: E/AndroidRuntime(348):  at android.app.ActivityThread.main(ActivityThread.java:4627)
12-11 02:45:59.232: E/AndroidRuntime(348):  at java.lang.reflect.Method.invokeNative(Native Method)
12-11 02:45:59.232: E/AndroidRuntime(348):  at java.lang.reflect.Method.invoke(Method.java:521)
12-11 02:45:59.232: E/AndroidRuntime(348):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
12-11 02:45:59.232: E/AndroidRuntime(348):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
12-11 02:45:59.232: E/AndroidRuntime(348):  at dalvik.system.NativeStart.main(Native Method)
12-11 02:45:59.232: E/AndroidRuntime(348): Caused by: java.lang.InstantiationException: com.ass.ui.Settings
12-11 02:45:59.232: E/AndroidRuntime(348):  at java.lang.Class.newInstanceImpl(Native Method)
12-11 02:45:59.232: E/AndroidRuntime(348):  at java.lang.Class.newInstance(Class.java:1429)
12-11 02:45:59.232: E/AndroidRuntime(348):  at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
12-11 02:45:59.232: E/AndroidRuntime(348):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2577)
12-11 02:45:59.232: E/AndroidRuntime(348):  ... 11 more

这是我的Logcat错误，下面是android清单文件。昨天工作正常，我还没有更改一个字母，该错误现在仍然存在。

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.ass.ui"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="18" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.ass.ui.Main"
            android:label="@string/app_name" >
                <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name="com.ass.ui.Settings"
            android:configChanges="orientation"
            android:label="@string/app_name"
            android:noHistory="true"
            android:screenOrientation="portrait" >
        </activity>
    </application>
</manifest>

似乎我看不到我在哪里错了。Tnx寻求帮助。