2 MSIL DLL embedded in a C# project

Hello, Sorry if my question is a bit futile, i am new in DotNet compilation/programmation...

I create a first MSIL DLL with ftn95, called A (with a VS2010 ftn95 project).

I create a second MSIL DLL with ftn95, called B (with a VS2010 ftn95 project), including a subroutine fB which calls a subroutine fA from the dll A.

I create a main class in C# (vs2010 project), which calls the function fB (which calls the function fA), adding A and B as references.

I have an error at the execution : '29: Call to missing routine - fA'

So he found fB but not fA. It is confirmed by a sentence before the error message, which says approximately that it wants to go step by step into B.fB, and then into B.fA : it is the problem, because A is in fA, not in fB !

Do you have any idea about this ? (I tried to add A as reference into the project B, but VS2010 crashes ...)

Thanks a lot !