My workaround:
0. Backup ~/.gconf/apps/panel
1. Press ALT+F2, type gconf-editor, press Enter
2. Expand [apps / panel / applets]
3. For every item in [apps / panel / applets] replace toplevel_id - if the value is top_panel_screen0 change it to bottom_panel_screen0; if the value is bottom_panel_screen0 change it to top_panel_screen0
4. Do the same for [apps / panel / objects]
Confirmed this annoying bug in Ubuntu 8.04.
My workaround: panel_screen0; if the value is bottom_ panel_screen0 change it to top_panel_screen0
0. Backup ~/.gconf/apps/panel
1. Press ALT+F2, type gconf-editor, press Enter
2. Expand [apps / panel / applets]
3. For every item in [apps / panel / applets] replace toplevel_id - if the value is top_panel_screen0 change it to bottom_
4. Do the same for [apps / panel / objects]