navigation problem in Blender 2.57.1


I just make my first steps in Blender and I have a problem with navigating with keyboard shortcuts.

With the numpad keys I can move up and down, to the left and to the right and I can rotate around an object but only in the up and down direction. I didn’t find a way to rotate around an object in the left and right direction.

The numpad 4 and 6 keys only rotate the object so that the object stays in the current view. But I cannot move around the object.

I tried to change the orbit style in the user prefs from Turntable to Trackball and backwards but there was no effect.

How can I enable the horizontal rotation around an object? No tutorial I read does mentions this (,,!