Look what happened:
And it happened with 256 stitches on my needle too. Just busted straight through. That's two of my Denise cables which have given out on me. I should send in and get them replaced. Of course, I've had the set for *does math* at least 4 years and it has seen some use. Don't worry though, I was able to save my stitches and transfer them to a different size 7 needle.
The Denises have fallen out of favor with me, as more of my projects are on smaller needles with thinner cords. Who knows, maybe I'll get a set of knitpicks options for Christmas. ;)