I've been running in New Balance Minimus trail shoes for about a year. I was in Vibram FF for a few months before I switched to the NB (I didn't like the "toes"). Just this December I started to get an occasional sharp pain in the arch of my left food. It started when I was running fast down a concrete ramp between trails, and typically happens when I am running downhill. The pain feels like a stretching/stabbing sort of pain, enough that I have to stop running or significantly change my gait. It can be mostly alleviated if I do more of a flat-foot strike with my left foot, and will eventually go away until I hit another downhill. My arch doesn't hurt to the touch, and the left arch doesn't feel any different compared to the right when I put pressure on it with my hand. Something to know about my past medical history that might have something to do with the issue I'm having now: I've sprained my left ankle three times. The first two times were minor, enough to stop me running for a week or so, but nothing too serious. The third time (August 2007) was very severe, requiring a hard cast for three days, crutches for a week and an air boot walking cast for two to three weeks after I got the hard cast off, then a sturdy brace for another two weeks, and no running whatsoever for eight weeks. I did plenty of physical therapy and got the ankle back up to the best it'll be, and it has been well-tested on some pretty rough terrain, though it still makes popping noises and will ache after a long run. I don't know if that has anything to with my foot pain, but I thought it might be worth mentioning.