So it sounds like you're trying to stream a video stored on a server, correct?
Here's the way the URL must be written:
"The URL must point to a file that ends in the appropriate file extension; for example, http://www.fakeURL.com/videos/Intro_Video.f4v for a file on a web server. Use rtmp:// in the URL for a video on the Flash Media Server or Flash Streaming Service."
This is from an article I wrote for InDesign Magazine on placing video into InDesign.