Unwanted Horizontal Scrolling

I use a Microsoft Wireless Optical Mouse and I've found that sometimes when I'm using the scroll wheel trying to scroll up and down a zoomed image in Photoshop it scrolls horizontally.

Why is it doing that and what can I do to make it stop and only scroll vertically?

I've seen it happen too Alissa, when I scroll too fast sometimes. It started in version 7 right after they 'fixed' the way the wheel works in an image.