The problem has been resolved now. I tried all the options you suggested but could not succeed. Then I tried a trick..
I created a new project suite and added a project. When I tried to map the objects of my application, It was mapping as a WinObject. So I transferred all the script files, Name Mapping and event files in the new project and TC started identifying my application objects as WinObject. I have not changed any settings of Test Complete before or after creating new project.
It's working now and I am able to run project successfully :)