F# Namespace not defined

Question

my F# project, working up til now, started erroring on:

Error 54 The namespace 'Vision' is not defined

I've include some images from Visual Studio that show the situation:

SO, I don't get why this built before and now won't build. The refs are there, the namespaces are in the refs. What am I missing?

Answer 1

@brent - bingo. I had it a .net 4.5.2 but the assemblies only support 4.5