I was down in so. cal for winter training this weekend and my 10-speed dura-ace front derailler ceased to shift for no apparent reason in the middle of a training ride. It simply wouldn't budge out of the big ring.

Today I removed the derailler from the clamp ring and noticed that the tension spring was loose and there was no tension whatsoever. Turns out that one of the two metal sticks that protrude out of either end of the derailler coil had snapped out of place. It locks into a groove on the derailler body. Somehow, it had snapped out of place, leaving the spring uncoiled and loose and lacking in any tension at all.

With great force, I was able to push the spring back into alignment and the derailler now works, but I am concerned about that happening again. I didn't hit any major pot holes, and was not in a crash, so I don't know why that would happen. Has anyone else had trouble with this? Is this a common problem with the new DA front detaillers?

I've neither experienced nor heard of this problem. Hopefully it was an assembly oversight and you've corrected it. However it might be worth visiting your lbs and comparing another DA 10-speed front derailleur with yours to ensure all's OK. Normally Dura Ace and Record stuff is trouble free, but, while as I said I'm not aware of a front derailleur malady as you've described, there are other rare malfunctions. If it repeats I'd consider it a warranty issue. Good luck!

Definitely look into warrany claims. You have a year from purchase on most shimano stuff.