It's reproducible. I've rebooted several times and it happens every time. I don't do anything special just open windows. I do have 2 identical displays in an over under configuration - the primary as far as the driver/board is concerned is on the bottom by default and I have them mapped the other way - it took me a while to figure out how to get the OS ( the nVidia propietary driver display app) to map them this way. maybe the confusion is that the secondary display is mapped to the top of the X window? maybe it's only partly mapped this way and the software is confused about where the windows and the displays are. As I said I have a workaround but it's annoying. Sometimes the workspace1/workspace 2 doesn't work but moving the window off the lower edge of the bottom display ( the primary) and back on fixes thing - the button in the panel reappears Thanks for getting back to me On Mon, Mar 28, 2011 at 5:10 AM, Sebastien Bacher