lets say for the last 2 years i have been able to connect and host to all the people i have come across (although i have adsl 1 the host isnt the best). ever since yesterday i have come across aprox 8 people who i play with on live regularly and for some reason i cannot connect to these people any more.

i have tried restarting my modem several times and even turned my xbox and modem off for 2 hours and over night and still i have the connection problem.
i have no idea what is causing the problem but as far as i am concerned i should be able to connect to them as my UPnP is enabled and my gateway firewall disabled allowing all trafic through.

any idea why i cannot connect or host now?
any input appreciated. cheers.