Oh yeah! You never forget! Equipment failure is a *****. My second collarbone break was the result of a broken crankarm during sprint intervals.
The crankarm failure occurred at the pedal spindle threaded hole. I checked the broken bits of the crank and found dirt in the beginning point of the crack, and as it propagated over time it finally gave out. There may have been a slight imperfection on the surface of the shoulder that mates to the pedal spindle, and that's where the crack started. I check my crankarms periodically now for this condition.
The sprint was all out on a small berg, and when the crankarm broke I fell on top of the handlebars and was zig zagging trying to correct. For a moment I thought I was going to make it but it wasn't meant to be. In slow motion mind you, I'm thinking ok, I'm falling and I'm going to land on the shoulder that I broke a year ago!
After the fall I jump up in denial. But then needed to sit right back down and wait for transportation.
Check your equipment!