Android i-mobileのエラー

Android開発をしています。
謎のエラーが出ました。
エラーはこちらです。

lang
104-15 11:26:30.698    7309-7327/com.ora_nge.pushplus E/AndroidRuntime﹕ FATAL EXCEPTION: Thread-217
2    Process: com.ora_nge.pushplus, PID: 7309
3    java.lang.NoClassDefFoundError: Failed resolution of: Lcom/google/android/gms/ads/identifier/AdvertisingIdClient;
4            at jp.co.imobile.sdkads.android.s.run(Unknown Source)
5            at java.lang.Thread.run(Thread.java:818)
6     Caused by: java.lang.ClassNotFoundException: Didn't find class "com.google.android.gms.ads.identifier.AdvertisingIdClient" on path: DexPathList[[zip file "/data/app/com.ora_nge.pushplus-2/base.apk"],nativeLibraryDirectories=[/vendor/lib, /system/lib]]
7            at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)
8            at java.lang.ClassLoader.loadClass(ClassLoader.java:511)
9            at java.lang.ClassLoader.loadClass(ClassLoader.java:469)
10            at jp.co.imobile.sdkads.android.s.run(Unknown Source)
11            at java.lang.Thread.run(Thread.java:818)
12    Suppressed: java.lang.ClassNotFoundException: com.google.android.gms.ads.identifier.AdvertisingIdClient
13            at java.lang.Class.classForName(Native Method)
14            at java.lang.BootClassLoader.findClass(ClassLoader.java:781)
15            at java.lang.BootClassLoader.loadClass(ClassLoader.java:841)
16            at java.lang.ClassLoader.loadClass(ClassLoader.java:504)
17            ... 3 more
18     Caused by: java.lang.NoClassDefFoundError: Class not found using the boot class loader; no stack available
19

おそらく、i-mobileを導入したのが原因と思います。
ソースがこちらです。

lang
1public class MainActivity extends ActionBarActivity {
2
3    static final String IMOBILE_WALL_PID = "38147";
4    static final String IMOBILE_WALL_MID = "165459";
5    static final String IMOBILE_WALL_SID = "439231";
6
7    @Override
8    protected void onCreate(Bundle savedInstanceState) {
9        super.onCreate(savedInstanceState);
10        setContentView(R.layout.activity_main);
11
12
13        ImobileSdkAd.registerSpotFullScreen(this, IMOBILE_WALL_PID, IMOBILE_WALL_MID, IMOBILE_WALL_SID);
14        ImobileSdkAd.start(IMOBILE_WALL_SID);
15
16        ImageButton btnNext1 = (ImageButton) findViewById(R.id.imageButton_1);
17        btnNext1.setOnClickListener(new View.OnClickListener() {
18            @Override
19            public void onClick(View v) {
20                Intent intent = new Intent(MainActivity.this, GameActivity.class);
21                startActivity(intent);
22            }
23        });
24
25        ImageButton btnNext3 = (ImageButton) findViewById(R.id.imageButton_3);
26        btnNext3.setOnClickListener(new View.OnClickListener() {
27            @Override
28            public void onClick(View v) {
29                Intent intent = new Intent(MainActivity.this, AsobikataActivity.class);
30                startActivity(intent);
31            }
32        });
33
34        ImageButton btnNext4 = (ImageButton) findViewById(R.id.imageButton_4);
35        btnNext4.setOnClickListener(new View.OnClickListener() {
36            @Override
37            public void onClick(View v) {
38                Uri uri = Uri.parse("http://ora-nge.com/Push/index.html");
39                Intent i = new Intent(Intent.ACTION_VIEW, uri);
40                startActivity(i);
41            }
42        });
43
44        ImageButton btnNext5 = (ImageButton) findViewById(R.id.imageButton_5);
45        btnNext5.setOnClickListener(new View.OnClickListener() {
46            @Override
47            public void onClick(View v) {
48                ImobileSdkAd.showAd(MainActivity.this, IMOBILE_WALL_SID);
49            }
50        });
51    }
52
53    @Override
54    protected void onDestroy() {
55        //Activity廃棄時の後処理
56        ImobileSdkAd.activityDestory();
57        super.onDestroy();
58    }
59
60}
61