There are several potential network problems. Have you disabled media sharing from tversity? You probably did but did you reboot your pc after installing PS3MS? You may have to allow PS3.exe through your firewall, you may also have to allow javaw.exe through your firewall. Depending on whose firewall you are using depends on how intuitive they are. None of the network settings in PS3MS should need adjusted and port forwarding is not usually required so you should not need to play with router settings. I would disable tversity and check your firewall settings first, if no luck post again and we'll try more.
Hopefully being helpful as this software is worth the effort