If you click the wrench icon on VoiceAttack's main window, then open the "Speech Engine" dropdown on the "Recognition" tab of the VoiceAttack options window, what is listed?
What is the value of the "Command Weight" and "Min Unrecognized Confidence Level" options on that same tab?
When you speak something that isn't a command, is there an "Unrecognized: " entry in the log on the main window, followed by what the speech recognition engine estimates you may have said?
Are you using the dictation mode (E.G. by executing a command containing a "Start Dictation Mode" action)?