I swapped cogs and apparently had not torqued the lockring enough. I was backpedaling a bit hard and the cog pushed the lockring right off the threads. I wasn't doing anything out of the ordinary, but I just F-ed the installation this time around. **** happens, I already ordered an IRO hub and I decided to try out Scrod's lockring.

Well, now I have a spare hub to use for a beater SS wheel with my dented Open Pro. I'm also going to the Rotafix/no-lockring idea that floats around.