KSH:

Let me start by saying I'm not a runner but I do suffer from "falling arches" as well as other foot aliments. I see a great foot doctor and have for the past several years been able to purchase affordable ($40) and very good inserts (Powerstep) for my shoes from him. When I learned my arches were falling (news delivered by chiropractor) I scheduled an appointment with my foot doc who added an arch support to the Powerstep inserts - problem fixed.

For some relief you might take a water bottle and fill it 2/3rds full and stick it in your freezer. Once frozen place it on the floor and roll your sore foot across it for 15-20 minutes.

I hope you find some relief.