OK, here goes.
project-bug-2.png - shows project selection, attempting to choose "z.vpj"
project-bug-3.png - shows result - "dx9.vpj" is still the active project. (Look at the "projects tab" on the left, the build choices don't update either in the Project Tools toolbar.)
project-bug-4.png - shows selecting "wgf2um.vpj"
project-bug-5.png shows that this selection worked.
Before you decide "aha! clearly z.vpj is bad!" I created it as a dummy placeholder this morning, when I realized I couldn't select "wgf2um.vpj" via the menu.
Using "set active project" via a left mouseclick menu from the "Projects" tab works fine in all cases.