Sounds like you have a problem with your codec files Sorry if you know this already but they are the small files that TVersity uses to translate the videos and music to a format that the PS3 understands hen they are being streamed.
The forums on TVersity web site will really help - do a search for the file type of the files that you want to play.
I found that the best thing to do was to uninstall all of the codecs I had already (found in control panel, Add Remove Programs) and install one of the packs of codecs on
www.free-codecs.com. People recommend ffdshow or this one:
http://www.cccp-project.net/
Good luck - took me a while to get it sorted!
Oh yes, nearly forgot. The other thing to do is in the settings panel, tell TVersity to always transcode, and pick the PS3 from the list of devices rather than have it automatically detect. That may help as well