In your VoiceAttack installation folder, do you have files named SharpDX.dll and SharpDX.DirectInput.dll in there?
If you don't, you'll need to install VoiceAttack again and make sure those files are present.
If you *do* have those files, there is something up with your setup, as the dll is trying to access some component(s) on your system and it is not working properly. Unfortunately, I don't have a solution for you as I'm not getting any reports like this from other users where I could establish a pattern :(
Thank you for the extra info, btw!