I sent an email to xbox customer support, They told me to ring xbox phone support, i rang phone support, they told me to post a new topic here because they cant help me,
Until a few weeks ago i had no problem with connection to games, hardly ever had any lag, and hardly ever had any connection problems when signing into xbox live itself during startup of my xbox.
Approximately 3 weeks ago i was playing Call Of Duty Black Ops, with my gamertag, and a friends gamertag signed in to play split screen, after a match we were invited to a party with a recent player from the previous game, when we joined we were both instantly signed out from xbox live, ejected from the game to the xbox dashboard, and could not sign back in, after about 5 minutes we were both allowed to sign back in, i reset the modem, and the xbox, after signing back in we noticed serious lag in almost all of our games, lost connection to hosts, had long waits while trying to join matches, this happened to a variety of games, Black Ops, Homefront, Naruto Storm 2, Halo Reach, Halo 3, GTA 4 (Original + TBOGT Multiplayer)
On top of that, My playercard for Black Ops, has automatically changed to my default rank, instead of the playercard i made myself... TWICE.
This has been going on the whole time since then, and again this morning i was signed out of xbox live, and couldnt sign back in for around ten minutes,
I rang my internet service provider last week, they said my internet connection is fine, the support rep i spoke to this morning when i rang xbox customer support asked me to do a speed test, and said that there is no reason why i should be experiencing lag while playing games because im getting very good speeds.
The Xbox Customer Support Rep, suggested that its highly possible i may have been hacked, i have already changed my password, but the problem persists, EVEN when the xbox is the only thing using the internet...
My housmate can play games with no hassles on his PS3