Wireless connection or heavy use on the network can be the limiting factor. Run wires if you can throughout your place otherwise you may want to give home network plugs a shot. They attach to a wall outlet and to your router. However Wired connection fixed all my stuttering problems and should fix yours and anyone elses as well as long as their system is powerful enough and the network isn't getting bogged down.
Core2Duo E8400 (@ 3.0), 8gigs of Mushkin, Vista Home Premium SP2 64bit, 2.5 TB of Space, Wired to Linksys WRT54G wired to 80GB MGS4 PS3 on Sharp 32" 720p LCD TV