calling WCF behind a H/W router

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WCF

Hi,
I'm calling a WCF service from a silverlight application. I need to expose the application to internet. So my network team configured a router with static IP (which is in net) and forwarded the url (say 192.168.0.15:451) to my local network. So when I call the static ip from internet, it is routed to the local ip(which is not visible to user), and I can access the silverlight application. In that application, I've called WCF, which is giving trouble.
When I call the WCF url directly from browser, I get the XML displayed(methods exposed by that service). But when I try to call a method, I'm getting a blank page.
What could be the problem or what I'm missing?
Thanks in advance...