This bug has been reported on Ubuntu Launchpad as:
From the launchpad report:
Placing a gnome window list in an xfapplet is fine until the number of open windows grows and the xfapplet expands, pushing everything to the right of it (switcher, notifications, clock, logout) off the screen. Unfortunately, the xfce4-panel tasklist currently caannot switch compiz 'desktops' when a window from another desktop is clicked (but gnome window list in xfapplet handles the desktop switching correctly.)
One possible workaround would have been to change the window-list-applet maximum_size parameter in gconf, but this parameter was deprecated in gnome 2.20.
I'm running xfce4-xfapplet-plugin 0.1.0-3ubuntu4, on Lucid: 2.6.32-22-generic #33-Ubuntu SMP x86_64
I can reproduce the bug using the gnome-panel directly, so not sure this has to be handled by the xfce panel.
Mass-reassign all bugs from florian@ to goodies-dev@, thanks for the maintenance work! (and sorry for the bugmail spam..)
Closing all xfce4-xfapplet-plugin (archived/deprecated/unmaintained project).