Hello feng,
Let me start from the end. "Reference source not found" is shown because processing is paused inside library code. By default, all x-ware you add to the project (ThreadX, GUIX, FileX, USBX and NetX) comes as pre-compiled libraries to reduce build times. You can add source to your project if you'd like to, but this will extend your build time.
As for the ping problem, try to set drive capacity to medium, as described in this post: renesasrulz.com/.../6582.aspx
Regards