the game works well without vorpx, but with vorpx, the g3d is ok, but the game goes in slow motion! really slow! why? ah, the game menu goes well, no slow motion, only in game.
ALT+TAB out of the game and back into it. That will almost certainly fix the issue. Alternatively you could use a tool like D3DWindower to force it to run windowed.
Incidentally I noticed the same doing a few tests recently. Couldn’t really find the cause, the next vorpX will at least show a notification the recommends the ALT+TAB workaround.