I use a dual-head setup with two separate screens (:0.0 and :0.1), so NO Xinerama or anything like that. Each screen has its own desktop chain (6 each). The problem is that if I press the desktop switching hotkey, the desktop switch happens on the screen with the currently focused window, instead of the screen where the mouse pointer is in. This might seem innocious, but it's in fact frustrating since in order to be able to switch the correct screen I have to *find* a window in that screen and move the mouse pointer over it first before pressing the hotkey, or click on the desktop of that screen before pressing the hotkey.
That makes perfectly sense and is pretty easy to fix too. I'll commit a fix tonite.
I've committed a fix in rev. 24372. Can you try? A snapshot is available from here: http://www.xfce.org/~olivier/preview/
I just tried it, it works perfectly, thanks :)