I have been streaming downloaded movies to PS3 for a while now but suddenly the new movies that I downloaded don't work. It comes up with an error that reads "Media Server Error: A network error has occurred. (00000000). I am currently using Windows 7 have only started having this problem within the last couple days.
The majority of the time this error comes up because the folder they're in isn't shared. Occasionally though it can be caused by windows media player losing sync with device. If the latter is the case you just need to resync it.
An even less likely culprit is the firewall. Some people will tell you to turn it off but this is NOT necessary. Just check it make sure sharing is properly enabled.