I have my Xbox 360 connected through ethernet cables to my D-link router (DI-524) which is connected to my PC running Windows XP. I have no problems accessing the internet on my PC or Xbox Live on my Xbox 360. The problem I have is with limited connectivity on Xbox Live. I noticed this when playing Crackdown with my friend, I was unable to join his game through a personal invite, or send my own personal invite due to "limited network connectivity issues". I have no problems searching for games through online systems (eg. Gears of War search systems are fine and I can connect to the games there), only problem I have is with accepting personal invites to games. I cannot accept or inniatiate chat invites due to the same issue I beleive.
I have updated my firmware on my router, tried disabling all my fire walls, tried opening up some ports with still no luck. I even reset my routers factory settings with no luck. I am not sure if it is an Xbox setting that is wrong or something to do with my router/firewall that isnt allowing other people to access my computer/360. Any help suggestions would be appreiciated.