Are you using the factory default firmware for the FIRST firmware? I guess the former otherwise you might already know about bdc-comm.
The CD with software for the Jaguar (*non* FIRST) can be downloaded here:
http://www.ti.com/tool/rdk-bdc24-cd
On it should be the stock version of bdc-comm which is a Windows application that lets you communicate over a serial connector to the Net/Serial connector of a Black Jaguar via adaptor. See the Getting Started Guide for more info.