I have removed all plugins, and disabled java, javascript and cookies.
I have also disabled images and link prefetching. None of these changes fix the
problem.
On the same site I found a page that scrolls even more slowly:
http://www.dailytech.com/German+Scientists+Declare+Speed+of+Light+Broken/article8487.htm
New observations after further testing: First, I think I was mistaken, and this
problem does not occur in my other Etch system. Secondly, top shows only one
CPU pegged at 100%, while the overall CPU utilization is 50%, suggesting that
the other CPU is idle. Taken together these seem to suggest a possible SMP or
motherboard issue (MSI K9MM-V).