Runtime Error 49, Bad DLL calling convention

Question

Q. Excel keeps throwing the following error, whenever my addin is loaded (Runtime Error 49, Bad DLL calling convention)

Answer 1

In my case this was "caused" by an excessive use of the continue character _ in a single if conditional

I had already recompiled, checked all return codes, moved modules around ,restarted excel , restarted my computer, copied the code to a brand new Excel spread-sheet, I read this article and the bit about return codes made me think about how many returns can be in an if statement

I had this

    If CompressIntoOneLineON(rg1, rgstart, rgend) or _
       CompressIntoOneLineOS(rg1, rgstart, rgend) or _
       CompressIntoOneLineOGN(rg1, rgstart, rgend) or _
       CompressIntoOneLineOGS(rg1, rgstart, rgend) or _
       CompressIntoOneLineGO(rg1, rgstart, rgend) Then
       <code>
    End If

I was getting the error when the subroutine containing this code exited So I changed to this

matched = True
If CompressIntoOneLineON(rg1, rgstart, rgend) Then
ElseIf CompressIntoOneLineOS(rg1, rgstart, rgend) Then
ElseIf CompressIntoOneLineOGN(rg1, rgstart, rgend) Then
ElseIf CompressIntoOneLineOGS(rg1, rgstart, rgend) Then
ElseIf CompressIntoOneLineGO(rg1, rgstart, rgend) Then
Else
  matched = False
End If
if matched then
  <code>

and the error went away

Answer 2

I had a similar issue, on my development PC it was working just fine. Funny thing was I had two separate calls to the same routine, one worked and the other didn't. On a production PC, kept getting the error. Tried renaming the routine, changing the parameters, parameter types to no avail.

What worked for me was to move the failing calling routine into the same module as the called subroutine.

The routine that was working previously was already in the same module.