invalid - Cannot resolve method _____ canddidates are: ____ in class ___, ____ in class ___

As I posted in my previous post, i have an inheritance chain of A : B : C

I have 2 extension methods that cover this A, and this C.

If I invoke the extension method for this C from a typeof(B) it will display this error. Once again it seems to do with inheritance chains not being evalulated at all, let alone just the first ancestor.

R# 6.1 Windows 7 x64 12GB ram VS2010 Ultimate SP1.