The "top" program reports that a single instance of xfce4-eyes-plugin (4.4.1-0ubuntu1) constantly uses more than 65% of my CPU, and indeed, having three instances of this plugin running causes my computer to become extremely slow. This is on a Dell Latitude E6420 with a Intel Core i7 @ 2,2 GHz that otherwise works quite well and fast. I am using xfce4 since I upgraded to Ubuntu 11.10 yesterday. Under Ubuntu 11.04, I used to have 3 instances of the Gnome2 eyes plugin, which did not lead to such au CPU usage. I am using the plugin with the Tango theme if that matters.
I cannot reproduce this on two machines with different hardware. CPU usage is around 0.7% when moving the mouse and causing redraws on a machine that is much older than yours. I'm sorry, I can't think of anything that would help you.
Changing from invalid to worksforme. Invalid is so very red and unpleasing to the eye...