Suddenly, for no good reason at all, my scrollbars started misbehaving. A new computer doesn't constitute a good reason, especially since both the new and the old one are running Ubuntu Lucid Lynx with KDE.
It was absolutely nuts. Usually, when I drag a vertical scrollbar up and down, the horizontal movement of the mouse doesn't make a difference. I can understand a system that would stop scrolling if the mouse gets too far away. There is absolutely no excuse for jumping back to the initial point when the mouse gets too far away, which is what it did.
Turns out it depends on the widget style, but is not mentioned in any widget style description, nor in the fine manual. Finding the appropriate widget style by trial and error was easy, but I am still annoyed.
That's the problem with the new KDE: lots of configurable stuff and no place to configure it. I mean, having themes is nice and all, but the user should be able to configure anything the theme creator can configure, without having to read a manual on how to create a theme. I much rather quickly choose a theme that seems nice and reconfigure the few things that I don't like than wade though hundreds of themes looking for one that fits my specs the best.
Some things (the color themes, for example) actually work that way, but most don't.