Please describe the problem:
If any widget on the Gnome Panel has an associated theme style which contains an 'engine "smooth"' declaration, portions of the panel will not become transparent when set in Panel Properties.  



Steps to reproduce:
1. Select a gnome theme which contains the "smooth" engine in a style which is applied to or inherited by any widget contained by the Gnome Panel
2. In the Properties for the panel, click the 'Background' tab and choose the 'Solid Color' radio button.
3. Select anything less than 100% opacity on the slider control.  


Actual results:
Only portions of the Panel which are not styled by the "smooth" engine will become translucent.

Expected results:
The entire panel, including menus, whitespace surrounding notification icons, and similar should become tranlucent.

Does this happen every time?
Yes

Other information:
(please bear with me this is my first ever bug submission)  Please email me if clarification is required.