copy scroll very very very ... slow

Suppose I want to copy a big multi-screen portion of a mail message to paste into some document. I click and hold near the top of the region and then move the mouse pointer down to highlight that region, all the way down to the bottom of the screen to scroll. Blam. Scrolling proceeds at a rate of about one pixel per 5 seconds. On the other hand, highlighting a multi-screen-sized region from the bottom up is no problem, proceeding at an expected scroll rate. Is this a bug? Is it fixed in Leopard Mail?