First, grab the '03 service manual by clicking the "Buell Service Manuals" link at the top of the page and save on your computer.
Next, I'd check my battery terminals and Grounds that are handy to make sure they've not loosened up. Then I'd look up the Voltage Regulator in the Service manual. It's got a section on diagnosing & checking to make sure it's good.
Good luck & post up if you're not running soon.