I seem to have the same problem with my laptop (asus ul30a-a2 running debian testing, xfce 4.8, kernel 3.2.0-2-amd64; my mouse is an Evoluent VerticalMouse 3) The solution found here (https://bbs.archlinux.org/viewtopic.php?id=123553) is working for me so far. Essentially you edit /etc/laptop-mode/conf.d/usb-autosuspend.conf and add the usb id of your mouse to the blacklist.