Version:            (using KDE 4.1.0)
Installed from:    Fedora RPMs
Compiler:          gcc (GCC) 4.3.0 20080428 (Red Hat 4.3.0-8) 
OS:                Linux

I have a secondary screen attached to my laptop and use a dual-head configuration. I use `xrandr --output LVDS --right-of VGA' to put my laptop (LVDS) right of my external monitor (VGA).
The panel with the taskbar, icons of running applications and the clock, etc. is only visible on my laptop screen (in KDE 4.0 this was my external monitor, which I prefer). I put the panel at the top of my screen. 
On my external monitor there is no panel. However, I cannot use the topmost part of my external screen. It looks like the task bar panel is allocating space without being visible. I cannot drag windows to the top. Also when I maximize windows, the top rectangle (with the height of the panel on my laptop screen) is unused; I only see part of my background.
I suggest to put either the panel on both screens or not to claim the screen area on the screen not containing the panel. Also it would be nice to have the option to choose on which screen the panel should appear.