Did I screwed up my table (ME176CX)? Need advice...

HI,

When I swipe down on the screen of my rooted ASUS MeMO Pad 7 (ME176CX), select
"Settings" and then "Data Usage", "Settings" dies with the notification:

"Unfortunately Settings has stopped! [OK]"
(by the way: what's [OK] with this??? ;|

With calog I found this:
08-08 18:52:21.109 I/ActivityManager(731): Start proc com.asus.powersaver for broadcast com.asus.powersaver/.BootReceiver: pid=3581 uid=1000 gids={41000, 9997, 3003, 3002, 3001, 1028, 1015, 1023} abi=x86
08-08 18:52:21.149 D/AndroidRuntime(3350): Shutting down VM
08-08 18:52:21.149 E/AndroidRuntime(3350): FATAL EXCEPTION: main
08-08 18:52:21.149 E/AndroidRuntime(3350): Process: com.android.settings, PID: 3350
08-08 18:52:21.149 E/AndroidRuntime(3350): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.android.settings/com.android.settings.SubSettings}: java.lang.NullPointerException: Attempt to invoke interface method 'boolean com.android.internal.telephony.ITelephony.getDataE nabled()' on a null object reference
08-08 18:52:21.149 E/AndroidRuntime(3350): at android.app.ActivityThread.performLaunchActivity(A ctivityThread.java:2316)
08-08 18:52:21.149 E/AndroidRuntime(3350): at android.app.ActivityThread.handleLaunchActivity(Ac tivityThread.java:2376)
08-08 18:52:21.149 E/AndroidRuntime(3350): at android.app.ActivityThread.access0(ActivityThre ad.java:147)
08-08 18:52:21.149 E/AndroidRuntime(3350): at android.app.ActivityThread$H.handleMessage(Activit yThread.java:1281)
08-08 18:52:21.149 E/AndroidRuntime(3350): at android.os.Handler.dispatchMessage(Handler.java:10 2)
08-08 18:52:21.149 E/AndroidRuntime(3350): at android.os.Looper.loop(Looper.java:135)
08-08 18:52:21.149 E/AndroidRuntime(3350): at android.app.ActivityThread.main(ActivityThread.jav a:5253)
08-08 18:52:21.149 E/AndroidRuntime(3350): at java.lang.reflect.Method.invoke(Native Method)
08-08 18:52:21.149 E/AndroidRuntime(3350): at java.lang.reflect.Method.invoke(Method.java:372)
08-08 18:52:21.149 E/AndroidRuntime(3350): at com.android.internal.os.ZygoteInit$MethodAndArgsCa ller.run(ZygoteInit.java:899)
08-08 18:52:21.149 E/AndroidRuntime(3350): at com.android.internal.os.ZygoteInit.main(ZygoteInit .java:694)
08-08 18:52:21.149 E/AndroidRuntime(3350): Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'boolean com.android.internal.telephony.ITelephony.getDataE nabled()' on a null object reference
08-08 18:52:21.149 E/AndroidRuntime(3350): at android.telephony.TelephonyManager.getDataEnabled( TelephonyManager.java:3449)
08-08 18:52:21.149 E/AndroidRuntime(3350): at com.android.settings.DataUsageSummary.onCreateView (DataUsageSummary.java:382)
08-08 18:52:21.149 E/AndroidRuntime(3350): at android.app.Fragment.performCreateView(Fragment.ja va:2053)
08-08 18:52:21.149 E/AndroidRuntime(3350): at android.app.FragmentManagerImpl.moveToState(Fragme ntManager.java:894)
08-08 18:52:21.149 E/AndroidRuntime(3350): at android.app.FragmentManagerImpl.moveToState(Fragme ntManager.java:1067)
08-08 18:52:21.149 E/AndroidRuntime(3350): at android.app.FragmentManagerImpl.moveToState(Fragme ntManager.java:1049)
08-08 18:52:21.149 E/AndroidRuntime(3350): at android.app.FragmentManagerImpl.dispatchActivityCr eated(FragmentManager.java:1869)
08-08 18:52:21.149 E/AndroidRuntime(3350): at android.app.Activity.performCreateCommon(Activity. java:5970)
08-08 18:52:21.149 E/AndroidRuntime(3350): at android.app.Activity.performCreate(Activity.java:5 977)
08-08 18:52:21.149 E/AndroidRuntime(3350): at android.app.Instrumentation.callActivityOnCreate(I nstrumentation.java:1105)
08-08 18:52:21.149 E/AndroidRuntime(3350): at android.app.ActivityThread.performLaunchActivity(A ctivityThread.java:2269)
08-08 18:52:21.149 E/AndroidRuntime(3350): ... 10 more

Is this with any MeMO Pad 7 ME176CX as it is a tablet and no phone or did I screwed up my tablet?
Since I am rooted and suppose I need to do a factory reset -- is there any tutorial on this or do
I only need to reboot into droidboot and select fectory reset?

Thank you very much in advance for any help!
Best regards,
tuxic

(PS: I did not remove any System App from the tablet.)