Media sharing; UPnP problems

Allright, I guess many of you who has tried to share something on the network via Windows Media Player has encountered this problem, as it seems like very many gets it. I have Windows XP SP3.

I have an Xbox 360 I would love to share media with, and I have been able to do it in the past, but when I tried last time (maybe 3 months ago last time I used it), it wouldn't let me start media sharing. All it would was just to freeze and then come back like if I had not done anything. This is not important, as I have isolated the problem: the service Universal Plug and Play is not working. Well, it starts but then it stops instantly with the message "The Universal Plug and Play Device host service on Local Computer started & then stopped. Some services stop automatically if they have no work to do"

I've been googling alot to solve this, and no working answer for me yet. Seems like my case is special or something.

What I have tried so far:
- Checked the registry for that LOCAL SERVICE has all permissions on HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\UPnP Device Host, and it's underkeys
- Reinstalled UPnP service
- I had the HTTP SSL service started (set to manual), the SSDP
Discovery Service started (set to manual)

Now I have no clue left. Help would be greatly appreciated.

 

Oh, and I haven't changed any hardware as far as I remember.