Wacom Bamboo + Win7 = notchy/has lag

I've had my new Sony Vaio since Christmas and it's quite annoying. When I'm using my Bamboo graphics tablet in Photoshop and want to either zoom in or use the bottom click to move across an image, the action has a massive lag and isn't smooth and precise, like it was on my old budget laptop from 2005. It's so poor that I don't even use the tablet for zooming in any more - I just use the zoom keystrokes on the keyboard (which take longer and shouldn't have to do). What can I do to have the graphics tablet working as it should and might it be the Win7 OS that is causing this?