Vista/WMP11 Problem Sharing Media to PS3

It seems as if something is going wrong with windows vista installed in my system. I have set up windows media player sharing to my Sony Playstation 3. I have made sure that I have correctly configured my system and network sharing and UPnP services are getting started automatically but i don't know why PS3 is still getting recognized as "Unknown Device" in "Media Sharing" window. Even though i have allowed share media in my "Private Network." When i try to search for a media server through PS3 than it reports "cannot find a media server." I have carried out further trouble shooting and have found that "Network and Sharing Center" window in vista changes my "Private Network" setting to "Public Network." and turns OFF "Network Discovery" because of which PS3 fails to locate the media server. I never had any issue in using the same set up with windows xp and somewhere i feel hat there is something wrong in vista and not the way i am setting up things, has anyone here faced any issue like this???

Have you turned off IPSEC ? If not, than turn it off now and cross check your setup. Other than that make sure that you are having recommended windows update installed on your system.

I have turned off IPSEC and my system is up to date with all recommended updates installed. I have been looking after a fix for this issue since when, but i haven't found one. I have checked out several forum and have gone through their discussion thread and have raised few question there as well but no one is able to to find out the unknown reason why Vista is turning off Network Discovery and searching for Public Network. Ill carry out my search further and until than if anyone here has suggestion for fixing this issue than please let me know.