On a default xfce 4.8 installation, trying to remove the top panel (Panel 1) always results in a crash. Currently, there is no way to remove that panel. I'm away from that particular machine so I can't provide any debug info right now, but this should be quite easy to reproduce.
Well obviously I don't have that problem so you need to give me some debugging information. A backtrace would be nice and the output of "xfce4-panel -q && PANEL_DEBUG=1 xfce4-panel &> ~/panel.log", run inside a terminal.
Created attachment 3372 Debug log
Comment on attachment 3372 Debug log I hope this is helpful.
Yes it was, fixed in 8b0c024.