The plot: explorers find a planet, it has lots of metallic structures that exhibit regularity and pattern, but apparently nothing living. The explorers feel very secure - they have lots of force-fields etc. to keep them safe. However they start disappearing, and it becomes clear a swarm of metallic creatures inhabit the planet that are somehow wiping peoples' minds. The story ends with most/all of the explorers dead - a hubris tale.
Would love to find the story again, can't Google for clashes with plots of grey-goo stories/nano technology research!