While likely unrelated to the issue you're experiencing, your VoiceAttack version (v1.7.8) is quite old (it came out over a year and a half ago) and out of date (the latest full release is v1.8.7), so you should really update it (an installer can be found
here).
Enable the "Check for Updates on Startup" option on the "General" tab of the VoiceAttack options window if you'd like to be notified of available updates.
It's possible the Windows update re-enumerated your audio devices. Is the "Windows Speech Recording Device" option on the "Recognition" tab of the VoiceAttack options window set to the default device?
Have you enabled the "Disable Acoustic Echo Cancellation (could help with recognition)" option?