Ideapad Y570 - strange behaviour with sound loudness setting and touchpad [ Edited ]

[Zanza]

My recently bought Ideapad Y570 often, but not always shows the following strange behaviour:

- Sound loudness goes down to zero and when you try to raise it again by using the Fn+Right Arrow keys or by setting it in Windows it always goes back to zero by itself.

- Touchpad is pressed and in the Synaptics options screens I can see that it notices the movements and "clicks" correctly, yet the mouse pointer does not move at all

Both of these can happen right after system start or they might only occur later after the system has run for several minutes. 

I reinstalled the Touchpad software and the chipset software, but to no avail. 

Any idea what could cause this?

[Zanza]

Other stuff that is activated with the Fn-Key like switching to a projector or switching the Touchpad on and off doesn't work when the two symptoms above happen either. 

So my guess is that it is something related to Touchpad and/or the Fn-Key.