I have a theory*- it was a bike made for a sponsored team that used a "Burnett" logo (I'm sure the Cannondale logo was still displayed too) and it was returned to Cannondale at the end of a season- maybe the sponsorship ended, who knows- and they just repainted it to give to one of their MTB racers for training the next year.

*By theory I mean it's a total guess! Sure would be interesting to find out the truth though.