Hi there,
Can I just ask why you purchased software to allow you to authenticate via AD when this is included in OS X?
Also, though this may/may not be of any help, and I'm aware this is an old thread, removing all forms of power source (iMacs and MacBook's/Pro's) and holding down the power button for 30 seconds will reset their network card, often this can be a major issue in locking up, especially when on AD.
Regards.