This happens on all of my Thinkpads, W510, W520 and T540p. The Thinkpad integrated "mouse" has both a touchpad and stick. I use the stick and the mouse buttons (left, center(scroll), right instead of the touch pad most of the time. So the right and left buttons perform as a normal three button mouse, but the center (scroll) button instead of being like a mouse wheel that jumps is essentially "infinitiely variable" so that holding the center button and moving the stick will scroll up and down. What happens (and has been happening for a very long time) is that the scroll will "freeze". In many cases I've already loaded the page and am scrolling up or down within a region that is already loaded. The scrolling then freezes. No spinning wait indicator, just a hard lock up. After sometimes as long as 3-5 seconds (sometimes less) the page will then move again. I have "Use autoscrolling" and "Use smooth scrolling" enabled and "Use hardware acceleration when available" disabled, but none of these seem to matter. Suggestions welcome.