Very odd...I'm wondering mainly whether it's VoiceAttack itself or something external triggering when it starts, and I'm inclined to suspect the latter.
Could you try renaming the VoiceAttack executable and starting it? It'll start as a trial, but don't worry, it'll find the license when you undo the renaming.
I'm thinking if something is watching for the process name to trigger the hibernation, that may work.