Can you clarify whether sending mouse clicks to the game does work when triggered by a voice command, but not by a keypress?
Do other action trigger by keypress? E.G. if you set up a simple command that uses TTS to say "Yes it works" and attempt trigger it by keypress while the game is running, does that go through?
I've seen games(well, *a* game) that hook the keyboard in such a way that VoiceAttack's hook stops working in that game. The solution in my case was to start VoiceAttack after the game.