[Connecting to a Web Service using Flash] issue

Hey,
using kirupa’s tutorial " Connecting to a Web Service using Flash" i have added Flash Builder’s library into my flash project. I am using HTTPService class of Flex in my flash project. If I repeat this process in separate blank as3 file, its works perfectly fine. But when I only add the flex library in my working flash project, it stops working. No error, no warning. I am really confused. Where should i start troubleshooting? Just adding the library starts the problem, but when I add this in a new as3 flash file, it works fine. All settings are same in both files.