Zero success with Streaming to XBox 360

Hey everyone, I'm on the verge of tears over this!

I recently installed 7 (x64) RC on my desktop which I had been using, among other things, to stream movies, music etc. to my XBox 360.

Since installing 7 I've had no joy getting the XBox to even acknowledge the existence of the PC, either directly or through WMC, let alone stream anything. The PC, however, can see the XBox. I've made sure that the relevant folders have been shared and that the XBox has been 'allowed'.

I have a laptop (Vista 64) that can access the shared folders on the PC and can be seen by the XBox. I can stream media from the laptop no problem.

Does anyone have any ideas? Am I missing something really obvious? I really need help as I justified purchasing the XBox to my wife as a media streamer so that she can watch Desperate Housewives whenever she wants!

Partial Success!

I'm not sure how I did it, but the XBox is now acting as a WM Extender. Can't navigate around folders as it used to be able to though...

Anyway, if anyone is interested, the plugin 'Media Browser' makes WMC how it should've been in the first place; awesome piece of software.