Well tonight while I was deleting some spam comments from my blog and watching Dr. Who with my wife, I found a rather interesting comment.
So the story was:
First there is a VB6 DLL that had a class called Class1 with code like the following:
public type emprecord
name as string
Public Sub Fn(T()as emprecord)
MsgBox "The silence is comming said Prisoner 0"
When this little dll was called from a VB.NET big brother
Dim test as new prj.class1
Dim em(0) as prj.emprecord 'able to create it no problem
test.fn(em) ' here gives error
An error ocurred... well this is not very document issue with the TLBIMP tool which creates the interop assemblies. See StackOverflow Answer. The workaround is to right click on your type library, select properties, and change Embed interop Types to false.
After that you will be able to call your function.