I was installing new printer software today, and ran across an old enemy: serial progress bars. This is where a progress bar is shown, but when it hits 100%, the task isn't over, you just get another progress bar that starts over again at 0%. Sometimes there'll be five or six of them in a row. Doing this completely subverts the original goal of the progress bar. It was meant to give the user some idea of when an operation would be completed. By making the user suffer through a parade of identically-labelled progress bars, the user is left almost as baffled as if there were no bar at all (it's marginally better, because at least you can tell something is happening), but a spinning beachball would communicate the same thing without misleading the user into thinking that he's being told something useful.
Even worse, some of these progress bars are the lightning variety: they zip immediately to 100%, only to be replaced by another progress bar that flashes immediately to 100%, etc.