This is the button located between the left and right mouse buttons, just below the spacebar and just above the touch pad. The workaround/solution for this issue that I've found is to just press the middle trackpoint button on the laptop once.
The operating system I'm running is Windows XP Pro SP2. The issue has always seemed to occur when I'm sitting at my desk at work and the Thinkpad is in its docking station, and I'm working with the external USB mouse. If I manually scroll the document up by dragging the vertical scrollbar up with the mouse, the document scrolls back down again as soon as I release the mouse button to drop the scrollbar.
Two or three times over the past six months or so of daily usage of my Lenovo (IBM) Thinkpad T60 laptop, I've encountered an issue where the system seems to get stuck in a 'always scrolling down' state: in the active/foreground application, if the application has a vertical scroll bar, the document automatically scrolls to the bottom, even though I'm not touching the mouse wheel or otherwise doing anything that would cause the document to scroll.
