The dropping window problem is really common on GTVs. There are a series of rubber "bump stops" in the doors that set the angle and drop of the windows. They come loose over time and often cause the window to "sit out" from the rubber sealing around the door frame. You need to find a good garage that can tighten up the bump stops and set the windows up properly. Go to GTV6.com and try to find the link to this problem. Someone fixed it DIY some months ago (although it was a pain in the ass getting the door surrounds off!). Don't despair, it is a common fault, mine does it, but I just drop the electric window slightly and push it back up and it seem s to seal properly (will not work if driving fast as the external air pressure pulls the window out to stop it sealing properly).