我在Eclipse中创建了示例安卓项目，但在执行过程中收到错误：Activity类{com.example.best/com.example.best.MainActivity}不存在。

但项目中存在MainActivity类

package com.example.best;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

以下是控制台上打印的错误消息

[2015-03-01 22:01:58 - best] Starting activity com.example.best.MainActivity on device EAAZCY30C637
[2015-03-01 22:01:59 - best] New package not yet registered with the system. Waiting 3 seconds before next attempt.
[2015-03-01 22:02:02 - best] Starting activity com.example.best.MainActivity on device EAAZCY30C637
[2015-03-01 22:02:02 - best] New package not yet registered with the system. Waiting 3 seconds before next attempt.
[2015-03-01 22:02:05 - best] Starting activity com.example.best.MainActivity on device EAAZCY30C637
[2015-03-01 22:02:05 - best] New package not yet registered with the system. Waiting 3 seconds before next attempt.
[2015-03-01 22:02:08 - best] Starting activity com.example.best.MainActivity on device EAAZCY30C637
[2015-03-01 22:02:08 - best] New package not yet registered with the system. Waiting 3 seconds before next attempt.
[2015-03-01 22:02:11 - best] Starting activity com.example.best.MainActivity on device EAAZCY30C637
[2015-03-01 22:02:12 - best] ActivityManager: Starting: Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] cmp=com.example.best/.MainActivity }
[2015-03-01 22:02:12 - best] ActivityManager: Error type 3
[2015-03-01 22:02:12 - best] ActivityManager: Error: Activity class {com.example.best/com.example.best.MainActivity} does not exist.

以下是我的清单文件的内容

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.best"
    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.example.best.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

我应该怎么做才能解决这个问题？