Exposing .NET components to COM

Hello All,
I have god some problem in exposing .NET component to com.
The component written in C# and used in C++ 6.0.
The .NET component was build in VS2003 and works perfect.
After it we upgrade the project to VS2005.
The problems start when we add new functions to C# code.
The C++ application is able to see the new functions and make
successful calls but after it the exception is thrown and only
catch(...) can get it.
The call to old functions working fine without any exceptions.
Any chance anyone saw or met this issue?
Thanks,
Alex