hi guys i need some help here. i got xbox connect. first time i used it it was fine played someone across the country with no lag. then....BOOM. i play my friend--we both have 2700/256 cable connections and a ping of 70--and we have major lag on the end that is not hosting. i don't understand this. could it be my router? Here is my setup.

Computer and Xbox are going into a Gigafast EE-400R router which goes to a Toshiba cable modem. thats pretty simple. i forwarded all the right ports so i could host, and everything should be fine, right? WRONG as can be. i have no clue what do do to fix this. im gettin some pretty big packet loss and some serious lag. any suggestions guys?