360 As Extender - Audio And Video Error

I've been running Vista 64 sp1 about a year, and using my xbox 360 as an media center extender, hard wired. Its been mainly for pictures and music as we all know it's picky when it comes to video. It's been swell, no hickups at all. All this time, I've had a hauppage HVR4000 installed but not ever in use. Since all i have is analouge cable for TV-signal, I didn't have much use for it anyway, as WMC as of sp1 didn't support this type of signal.

A few weeks back I discovered TVPack2008, and suddenly realized I could put my HVR4000 to some good use. Since this update was OEM only, I had to find a rouge copy of the installer. Voila, analouge cable TV-playback on my 'puter.

Here my sorrows start:

Streaming to MCE (360) now only produced video or audio errors, saying I had to restart the extender. Pictures could still be viewed, but all video/audio nomatter what filetype, would no longer work.

So in my last desperate effort to get it to work again, I installed win 7 64, and was hoping for a change of luck. Same symptoms, different error message: "MCE cannot find the file you are trying to play". Pictures can still be viewed as before. The files are stored in default folders, and they are not corrupted. Streaming to dashboard works fine, both audio and video.

Also the "Play To"-functionality is not working, giving me error codes 0X80040369, UPnP-error 705, saying "cannot control the device".

What I've tried so far without luck:

-Updating firware on my D-link N router

-wiping the Xbox 360 harddrive and running intial setup

-opening up required ports on firewall (although I've read this doesn't do anything for devices on the same network)

-uninstalling hauppage drivers when using vista64 sp1.

My win 7 install is clean, no codec packs or funny stuff.

Anyone experiencing similar things? Or better, could give me some pointers to how to fix it?