No icons visible if panel is on side rather than top or bottom of screen

[Bill Trost]

I'm using window picker under the Ubuntu GNOME desktop on Lucid with the panel at the right side of the screen. When I put window picker in that panel, I don't see a panel. I do see a bit of shading that seems to be the full height of the available portion of the window, and if I hover the mouse over that shading I see a tooltip for one of the open windows. It's as though the window picker is drawing the icons left-to-right despite the fact that the panel runs up-and-down.

Uh, other details: 64-bit Linux...nothing else comes to mind.