Originally Posted by madpogue

Aren't the bolt holes drilled and tapped directly into the spindle? I guess I never looked close enough.

If it's indeed a case of initial loose fit as suspected, the BB itself is probably fine. Hard steel BB, softer aluminum crank arm, the BB wins and the arm loses. As for crank arm cost, switching to another technology would be expensive, but square taper cranks are easily had at any bike co-op. Depending on concern about weight balance and aesthetics, the OP could even opt just to swap that NDS arm, since the DS is single speed. Sourcing a single orphaned arm with no need to match it gets you into the "donation to the co-op" price range.

And +1 on the marine grease; it's water-resistant, and several LBSes around here swear by it. Available at any man-mall.