Never mind... a coworker just figured out that it does in fact work, but the development pane was collapsed against the left edge of the FireFox window. It is easy to miss the tiny little expander bar on the left edge - it looks like just an empty window. Expand the pane and all is well. I suspect that the state of this pane is not being saved reliably because I never collapse it (never realized it could be collapsed).
Thanks for the help.
-Mark
