Items “escaping” on scrollable taskbar

Maybe this is a known Windows XP annoyance, but I did not find it mentioned anywhere:
I have the taskbar fixed, double high, and this happens when there are so many applications open that the taskbar has more than two rows, and is scrollable. Every now and then, I want to click on an application icon on one of the lower rows to bring it into focus, but instead, the taskbar just scrolls up so I don’t see the icon anymore! I scroll down and click on it once more, then it comes to focus ok.
Any ideas?
Thanks, Leonardo