Windows 7: WMP Streaming Problem

Hi all:
I have 2 computers (desktop & laptop) setup for streaming media - also a net enabled receiver (Integra DTM-40.4).
All the devices can see each other. I can stream from the desktop to the Integra or to the laptop (via Windows Media Player).
However, when I try to stream from the laptop to either the Integra, or the desktop, I get an error. No error message from the desktop, but when trying to stream to the Integra I get "Media is not available" error.
From the Integra I can even see the playlists and songs on the laptop, but when I try to play it errors out.
All network/sharing settings appear correct (laptop same as desktop).
Who knows if the error message is correct, but if it is, it seems that the laptop is not reporting the file path correctly when sending.
Any ideas?
Thanks much.