the problem is detailed on this line:
05-13 08:14:15.138: E/AndroidRuntime(891): android.os.NetworkOnMainThreadException
"Network on Main thread exception". That means, you cannot make any network calls in the UI thread, because if you do, the UI stops updating.
What you have to do is to use some type of threading approach. A common one in Android is the AsyncTask: http://developer.android.com/reference/android/os/AsyncTask.html