test your connection and see what sort of NAT you are both getting - is this for any game - can you play different games ok? - need more info really

all the games we have we lag out we both got open nats i think let me check i will get back to u

both connected to a router - what ip's are being assigned to the xboxes - could try manually assigning addresses and turning dchp off for part of the range - as i said need much more detail

what connection speed atre you getting over the dsl what router ?

router please just tell me what i should do

well its difficult to tell you what to do if we dont know wahts wrong go to system settings - network settings and tell us what ipsettings, ip address, subnet mask and gateway dns setting etc you have - do this on both xboxs -

you should really supply us with more details if you really need help its verry difficult with very little details !!!!

This happened to my friend and we fixed but i cant remember illfigure it out and tell you.