Error in Sending Mail in Lotus 6

I made a little program in c# that works fine on notes 4.5 And 5when the program is run on a client using notes 6.0 produced the following error:

COM object with CLSID {29131539-2EED-1069-BF5D-00DD011186B7} is either not valid or not registered.

I registered the NLSXBE.DLL as someone suggested, but now the program produce the following error:

Object reference not set to an instance of an object.

I found out that I call the method not in the same order as they have o be called, but I didn’t quite undurstand.

How can I solve the problem… thanks Alex