To rule out the plugin causing this issue, you're going to need to disable plugin support (uncheck the "Enable Plugin Support" option on the "General" tab of the VoiceAttack options window, click "OK", click "OK", then restart VoiceAttack).
After that, you'll want to create a new, empty profile, and add a single command that presses the key to turn the lights on, then save and check whether the issue still occurs.