Several things can cause this, not neccisarily a bandwidth issue as far as your ISP subscription goes.
Can you log onto your pc and try logging into your netflix account from there? If so, do you experience the lag times there as well?
Do you have wifi? If so, is your router locked down, WEP? WPA? Make sure you dont have any rascals leeching your precious bandwidth. Log into your router, check the logs and boot anyone off that you dont recognize, then lock it down.
Your wii uses wifi? If so, how far away/how great is the signal strength to it?