I just found this topic only now :-/
Anyway, I wanted something similar and found out it is because of the compositor, so if you want to use xfwm, you can restart it without a compositor, like this: xfwm4 --replace --compositor=off (however, this will deprive you of the Alt+Fn+trackball zoom) - see DevTerm Tips & Tricks - #3 by garabik for the commands I use.