> Does anyone have any idea on what could be
> happening?  I've used this program in the past with
> no problems, but this is the first time I've tried
> to use the capture URL feature.


It's really hard to know what might be happening in your case here.  You might
want to check this guide:
<http://httrack.kauler.com/help/Form-based_authentication>

Could be your firewall blocking the HTTrack proxy?  Or some kind of javascript
on the form not working correctly?