Assuming you're using the website version (as opposed to the Steam version), chances are your config file has gotten corrupted somehow.
While the settings (as in, things you may have changed in the options window; Your profiles should still be intact) will likely be lost, you can re-activate VoiceAttack the same way you registered it initially.
You should have received an email on the email address you used to purchase your VoiceAttack license (usually this would be the email address associated with your PayPal account) containing your registration key.
If you cannot find the email, you can use
this form to retrieve your license information.