Many android users will have meet this message on your android phone one way or another. This usually happens when u press the *,# or + and the phone button to made the call. After u press the *,# follow by some numbers, it shows USSD Code is running and later the Connection problem or invalid MMI Code will appear.
HTC Desire HD is a fully customizable phone and you can tweak it using the settings to your likes. Do not worry if you have done the wrong things, as you can return it to the default factory settings. Pls take note that we are not responsible for any data deleted from your HTC Desire HD. This process may or