Problem using a reference in a WCF project...

See more:

C#

VB

WCF

.NET4

I've been having the following problem:
I have a WCF project, MyService, which references another project, MyProject. This other project has a Class called MyClass and I am passing it as a parameter to a WCF Method.
Now when I test my WCF service in a simple Console app I need to pass an Object of the type MyService.MyClass, but this Class is non-existant! It should be MyProject.MyClass.
I have checked that everything in MyClass is Serializable, so that should not be the problem.
So far the only thing I do is pass MyClass to a Method and nothing else. It does not call other Methods in MyClass whatsoever.
And actually, in my Console app I can instantiate all kinds of stuff from MyService that are actually defined in MyProject.
Why does my WCF service/Console app think that all those Classes belong to MyService instead of MyProject?

Edit:
I have the MyProject referenced in both service and client side.
What's more, this worked a few days ago. I made some changes to MyProject (not MyClass or any Class it uses though) and now it doesn't work anymore.
My ServiceContract looks as follows:

<ServiceContract()>
Public Interface IMyService
   <OperationContract()>
   Function DoSomething(mc As MyProject.MyClass) As Integer
End Interface

Here is the Service.

Public Class MyService
   Implements IMyService

   Public Function DoSomething(mc As MyProject.MyClass) As Integer Implements IMyService.DoSomething
      ' DoMoreStuff returns an Integer.
      Return SomethingCompletelyDifferent.DoMoreStuff(mc.DoStuff)
   End Function
End Class

MyClass is defined as follows:

<Serializable()>
Public Class MyClass
   ' Lots of Properties, all of which are serializable and
   ' contain nothing more than Strings and Integers and some Enums.
   Public Function DoStuff As AnotherClass
      ' Do stuff with non-serializable Classes and return a non-serializable Class
   End Function
End Class

SomethingCompletelyDifferent and AnotherClass stay within the Service and do not communicate to the client app. So I do not expect those to be the problem. My client app has a reference to MyProject and simply does the following.

Dim service As ServiceReference.MyService
Dim mc As New MyProject.MyClass
service.DoSomething(mc) ' Error here. Cannot convert MyProject.MyClass to MyService.MyClass.

Now where did it get MyService.MyClass from?