I updated my version of xfce recently and a very odd problem came along with it. I have dual monitors and after installing Arch and Xfce, everything was working as it should. I have a dual monitor setup with two different wallpapers on each monitor. When I updated xfce, the right monitor is now using the same wallpaper as the left monitor. I can clear the problem by going into my desktop settings, setting both monitors to use no wallpaper at all, save the settings, go back into the settings, assign each monitor a wallpaper and its back to normal... until I either reboot/shutdown/logout or open a fullscreen application on the right monitor. This happens with Amarok and Firefox but does not happen with the xfce-terminal. It seems as if the wallpaper from the left monitor is just sitting on top of the wallpaper for the right monitor.
On a side note, this is not version specific to xfce. I was running Gentoo and had xfce, the same problem came up with a version update. I moved to Arch, with the same version of xfce that I was using in gentoo, the problem did not occur until I updated xfce again. I've also tried deleting my xfce folder with my home directory and the issue still exists.