Removed "50 year old wrought iron handrail and balusters"????
(Just shakes head.)

I hope you sold it to an architectural salvage company. Someone is going to be in for a treat.

Trust me, no one would want these. They were very dated looking and in terrible shape (Bent scrollwork, too many layers of white paint caked on by the previous owners and all chipped up). The new bannister is a huge improvement.

I would also like to add that we also put trim molding underneath the treads ( where the tread meets the riser). Could this be the cause of the problem? It's only 2 or 3 steps that have developed a bad squeak.