In 'View->3D View Mode->3D Window Settings' you can set the transparency to 'off', then the next time you make a view of an elevation, the windows will be opaque. However, if you left the transparency on when you created the view, there is no way to redefine the view so the windows are opaque.
I created two views of the same section -- one defined when transparency was on, and the other when it was off. Sure enough they each memorized their own transparency setting.
The question now is, How do you redefine the transparency state of a view? There is no transparency option in the Settings, and I have tried setting the transparency, popping up the settings dialog, then clicking OK, but it won't redefine the transparency. Currently, the only way I can solve this problem is to delete the original view and define a new one. However, I have a drafter who has completely annotated an exterior elevation, and has the transparency in the wrong mode. I would prefer not to lose all the associative annotation.