Spent a lot of time trying to resolve this problem....

I have created a custom ASP.Net data grid that has resizeable columns and can be scrolled up and down with fixed headers. The scrolling up and down is done by having the datagrid inside one div and a second floating div on the right which is only as wide as a scroll bar but is forced to be the same height as the div containing the datagrid via some Javascript.

On most user's machines the scrolling worked fine. On a handful of other machines, the scroll bar would work by dragging the scroller or using the mouse wheel, but the scroll bar arrows and clicking on the non-bar region would not scroll.

I had the user log on to another machine and the problem followed them. If I logged on to their machine the problem didn't exist for me. It had to be profile related.

I got the Network Admin to dump me a copy of the user's profile for a non-working instance and another and compared them. This was fruitless.

Finally I went back to the user's machine and noticed they were running Windows Classic theme not XP. I switched to XP theme and things started working. What could be the problem with the theme?

That's when I notice the user had large fonts turned on. Turned it off and scrolling worked perfectly.

Turns out with large fonts, the scroll bar div was 1px too narrow and was displaying a horizontal scroll bar which stopped the arrows from working (for whatever bizzare reason).

Changed the width of my scroll bar div and it works perfectly.