Ah. That would likely still be the same issue. Bluetooth in general is problematic, especially on Windows.
If you can borrow a microphone to test with, that'd be the safest option.
Do you have another recording device that you can set as default, E.G. "Stereo Mix"?
Ctrl-click the wrench icon on VoiceAttack's main window to open the "Sound" control panel applet, which lists those devices in the "Recording" tab; If you have another device, select it and click the "Set Default" button, then restart VoiceAttack and see if that changes anything.
Theoretically, if you switch the default device away from your bluetooth headset, that should have the same effect as plugging in a USB microphone, for the bluetooth headset, at least.