PreferenceActivity used as main activity has strange animation

Question

Hi,

I have a preference screen (subclass of PreferenceActivity) set as main activity (opened when the application starts) on android 1.6 device/emulator. Anyway the animation android uses to open this activity is different from standard activity. It seems that two types of animation run concurrently: the usual fade animation and the right to left one. This is the code of the onCreate() method:

getPreferenceManager().setSharedPreferencesName("app");
addPreferencesFromResource(R.xml.preferences);
screen = getPreferenceScreen();

How can fix this glitch?

Thanks