There are lots of different keyboard layouts depending on which country you are in. For instance, if I am using a US keyboard and I use the Language and Text system preference pane to switch my Input Source to German then I end up with the " when I press the key that has the '@' on it. Other characters also don't match up right.
The first step is to determine which keyboard you physically have, then compare it to the various virtual keyboard layouts available. I suggest opening the Language & Text System Preferences, and enable the Keyboard & Character View option in the Input Sources section. This will add a small icon to the upper right section of your menu bar next to the date/time. The Keyboard Viewer acts like a virtual keyboard which you can then compare to the actual keyboard you are typing on. Verify that the 'Input Sources' information is properly configured for your style keyboard and language. If you somehow ended up with the wrong keyboard then I would give Apple a call.