workspace question

[Linda]

  I have a user who uses gnome-classic with 12.04 LTS and is 
just starting to use workspaces. Today when she tried to 
switch workspace she wound up with a screen with just her  
background no panels, menus or shortcuts. I had her try 
ctrl-alt-arrow but it just cycled through for screens with 
only her background. I just ssh in and restarted Xwindows 
but am wondering if anyone knows what could have caused it 
and of a different way to get an active desktop back.
                        Thanks
                         Linda