Peter, it sounds like a cracked spine. If I remember correctly, Yakaholic had this problem a year or two ago. I don't remember if he repaired or replaced it. Spines run about $20 and require a complete disassembly.
With your legs, you would definitely benefit from the latest V-2 upgrades. The drums are stronger and wear better, having glass filled nylon. They retain the crank arms better so skipping holes from flexing crank arms is virtually a thing of the past. The V-2 sprockets no longer wallow or have mast retention problems (as long as you use Locktite on them). No set screws to back out.
That doesn't mean they don't wear, it's just a lot harder to break the stuff than it used to be for someone with your strength! Keep in mind that many worn (and some damaged) parts can be reversed to present new wear surfaces (including drums with distorted pin holes).
Lets see -- things that have been upgraded in the past 3 years -- drums, chain/cables, sprockets, masts, splined drum shaft, crank arms, crank arm caps. Same spine though as far as I know.
After you tally the costs, you might consider replacing the whole Drive with an '09 and epoxying yours together as a spare. BTW, that set screw doesn't have to be tight, just snug and stable. Over tightening the Allenhead screw can pre-load and stress that area.
