That's because the latest drivers don't support your Intuos 2. Wacom drivers are unfortunately not unified like graphics card drivers are. If you actually look at the
drivers page, you'll see the last driver that supported your model was Driver 6.2.0-w4. Here's a direct link:
http://cdn.wacom.com/U/drivers/mac/pro/WacomTablet_6.2.0w4.dmg
Even though the driver doesn't say it supports Mountain Lion, it should work. Heck, I'm using an original Intuos (back when they were still made in Japan instead of China) and it seems to work alright under 10.8 using the ancient 6.1.5-2 driver.