The windows shade/unshade,and scroll up and down,uncontrollably. It even cycles the desktops like mad,so it seems that the scrollwheel may be the problem? I don't notice this in other apps,though. So i reckon it's xfce/xorg that's causing it. Are there like a deadzone-setting for the wheel in xfce/Xorg? Although it's wierd that it's shading/unshading windows,(i don't know the shortcut-keys for unshading)it looks like the scroll-wheel goes bananas. I use a logitech optical desktop,and I have used GentooX for over a year,and I have never experienced this before. Anyone got a clue? 
Sincerely
Chiron