Install JAP on the computer and try that, it bypasses proxy servers... So if you have a proxy firewall then it will work... If not then you must get ophcrack or cain & abel to dump the password hashes from the firewall and then crack the hash. If you do not have time to crack it then go to http://www.milw0rm.com and submit the hash to them so they will crack it for you.

Astalavista!