Hi guys,
after spending many hours around this problem, I've come up with a solution to my installation of Studio, hope this will work for you too.

That's what I've done:
1) uninstalled Studio totally that means:
- Uninstalled everything related to Studio, including its USB drivers.
- Deleted any folder left out after uninstall process.
- Run Pinnacle RegDelete version 8.x:
Pinnacle Systems - Product Support - Studio version 8 - Tools - Download Area
2) reinstalled my AUDIO card drivers (Creative SoundBlaster)
3) installed latest Microsoft Visual C++ 2008
4) installed Studio 9.0
5) installed Studio 9 patch:
Pinnacle Systems - Supporto prodotto - Studio Plus version 9 - Aggiornamenti Software e Driver - Studio version 9

That worked fine for me, hope this will help you.

Regards