You have a Windows 8 PC with a touchpad that supports two-finger scrolling.
At the Windows 8 Start screen, you use the touchpad and two-finger scrolling to scroll across the screen.
In this scenario, in rare cases scrolling may stop working on the Windows 8 Start screen. This includes using the mouse wheel, touchpad or dragging the scrollbar at the bottom of the screen for scrolling. Mouse or touchpad movement and the ability to launch apps is not affected. In addition, this issue only affects the Windows 8 Start screen and does not affect any applications.
To resolve this issue, perform one of the following actions to change the focus away from the Windows 8 Start screen:
Switch away from the Windows 8 Start screen by launching (or switching to) a Windows 8 app or the Desktop. Then switch back to the Windows 8 Start screen.
Drag and drop an app tile on the Windows 8 Start screen.