I have started labbing here and this is how it pans out:
6.03 OK
6.02 OK
6.1 Not OK
6.12 Not OK
6.14 Not OK
6.16 Not OK

So, the DLL stops working when Mirc moves up to 6.1. Looking at the update list I only see the following change that seems a bit suspicious:

31.Now using Visual C++ .NET 7.0 to compile mIRC.

Has something happened with the calls ?

Give this bitchin problem some attention. I cant believe it is happening to me!! cool