Ted,
The button should be the same on both toolbars. I tested the latest build today and both worked just fine. 25 minutes seems like a really long time to calculate one isoline. How large is your dem? If you use the two buttons on a small sample dem like the one from the SA tutorial data (9.3 data) does one take longer than the other?
Along the lines of gathering user feedback; What do you find useful about this button? Why would you want a single contour line as a graphic? Why not use the Contour or Contour List GP tools?
Regards,