Breaking driveshafts in an awkward location... ideas?

Just broke my second driveshaft in this exact same fashion. Not a result of any sort of big impact, as far as I could see. The wheel just popped off while the truck was going in a straight line. They're nearly brand new shafts, each seeing less than 45 minutes of runtime.

These pictures should do most of the rest of the talking:



Something tells me this may be related:


Any ideas?