How can I improve my Xbox LIVE connection?

I am currently connected with a 25 foot long Ethernet cable while I wait for my wireless adapter to arrive in the mail, and while I play Modern Warfare 2 I am getting lag when I move my right stick to turn my character. I have tried re-booting my Xbox multiple times and reconnecting both ends ofthe cable also. I have had no problems with my wireless PC connection from my router before. PLEASE HELP!