Coming from a culture where nudity is unusual, into a nude "situation" likely builds artificial ties -- as part of a shared experience, and all that. We associate vulnerability with nudity, and it's only natural to trust someone more if you see a vulnerable side of them.
However, it would makes sense that the context of the nudity should matter -- as in, even for someone who grew up in a clothed culture to be thrust into a nude situation, if he or she plays it off as no big deal, I doubt the nudity would have an effect on honesty. Humans can usually adjust to new conditions quickly. If nudity becomes a non-issue, it probably won't make a difference.