Why does the mouse pointer shake or jump around when I press the stick firmly?

Why does the mouse pointer tremble or disappear when I press the stick firmly? And even when I press the stick, the mouse pointer moves toward the direction which is opposite to that of the stick operation. Why is that so?

Firstly, check if the settings of the mouse pointer and stick have been changed. If the settings have been changed, please refer to the procedure to resolve the symptom.

(Procedure)
- Set the pointer speed to a slower level
1. Click [Start] -> [Settings] -> [Control Panel] and double-click the [Mouse] icon.
2. Select [Pointer Options] on the [Mouse Properties] window and set the pointer speed to a slower level by moving the slide towards [Slow] in the [Pointer Speed] box.

- Set the stick sensitivity to firmer touch
1. Click [Start] -> [Settings] -> [Control Panel] and double-click the [Stick] icon.
2. Select the [Sensitivity] tab on the [Stick Properties] window and set the stick sensitivity to firmer touch by moving the slide towards [Firm Touch] in the [Stick Sensitivity] box.

** For reference **
Microsoft Web page http://support.microsoft.com/support/kb/articles/Q267/1/39.asp