no xbox live connection

as of today (22/03/2011) i cannot connect to xbox live though my 360 elite. I have ran the network connection test everything is fine up until connecting to xbox live (xbox console connects to wireless router which connects to the internet but cannot connect to xbox live) The only type of help i got from my console was some info about changing my routers MTU settings. before trying this i decided to turn on my little brothers 360 to see if he was having the same problem but his xbox live conection is running fine (btw my router is connected to 2 pc', 2 360's and a laptop) so i decided that the problem must be coming from my xbox. has anyone else had this problem? is there a way to fix it or can i expect to be buying a new console soon? any comments or help would be appreciated. Thanks