On my system, it appears that when making multiple selections in lists,
scrolling is dramatically slowed down for each item selected : when 1 item is
selected, the scroll is still more or less fluid, but when there is more item
selected, the window becomes irresponsive for long seconds before finishing to
scroll. During that time, Xorg uses 100% of the CPU.

The problem appears by example on nautilus' list view, or in pan's messages
list. However, it does not appear in evolution's message list. With some GTK
themes the problem is inexistant (no problem with "Mist"), but with others it
is very present (like with "Clearlooks").

I have a nvidia GPU (GT218 [GeForce 210]), with the proprietary driver
(195.36.31).