Got a BD Immortal Pro CF bike back in March. Probably have about 2K on it, and love every minute. Well, at least until this morning. I was stopped at a stop light about 6:30 AM on my way for a metric century. The light changed, and as I started to pull away there was this god-awful "sprang" and the chain came off. I hobbled back to the curb, and what do you know. My Ultegra rear derailer was a mangled mess hanging off by the cable.

I've had no problem with the derailer save a minor adjustment after about 300 miles. There was not warning or other indications. I always down shift when I'm approaching a stop, so I was in low gear.

I'm about to call BD to arrange a warranty replacement. I'll keep you posted on how it goes.

Meanwhile I've got to call a buddy who has a spare RD I can borrow.

BTW, I walked home about 5 miles, put the pedals on the beater bike, pumped up the tires, and got in a good solo. Gotta go to www.RidewithGPS.com and map my route. I probably did about 50 miles.