issue while referencing a .net dll from a .net excel addin dll

Iam facing a peculiar issue when i try to reference a .net dll within a .net Excel Addin dll created
through Extensibility projects.

Whenever i try to create the object of the class in the referenced dll using new from the Excel addin dll ,the control
never goes to that particular function in the excel addin dll where the object is created when the addin dll is loaded by Excel .
But when i comment the code which creates the object using new ..and run it ..the control
goes to that particular function.

Is there anything which i will have to add additionally to make it work.
Please let me know.