Web Services and Inherits

I have a project with plenty of classes. All of them inherit from a common class. This works great for the current application in place which is ASP and does not use web services at all.

The thing is that, by using the very same logic, I need to build a "smart app" for some of the functionality that the ASP app provides. Then, I want to build web services so I can later create Visual Forms front end for such functionalities.

The thing is that when creating a web service that uses any of my class's methods .Net stack overflows.

Then, I tryed creating a simple class, no Inherits, and the web service works great.
Then, I created a very simple "common" class -just 1 property- and told the first one to inherit this simple "common" class. And yes, that is where it burns.

So, the question is, how can I build a simple web service, with a simple web method that returns a simple class instance which inherits from a simple master class.

I really need and answer to this issue, even if it is; you can't do it.

Thanks