Although there are faces and volumes in my Gambit model, neither faces nor volumes can be selected with the mouse (both select mode and shift-left mouse button don't work). Edges and vertices work as expected. All the other mouse actions like moving and zooming work ok. What to do? Saving and reloading doesn't cure the problem. It seems to be inherent to my model.

It could be that the faces and volumes were turned off. Click on the display attributes button (it's towards the bottom of the screen... looks like a read rectangle with check boxes). Select the volume and the faces option, and make sure the drop down says select all. Then towards the bottom make sure the visibile is selected and the option is on.

Hope this helps, and good luck, Jason