Downloadable content is gone

I had a bunch of full games downloaded from the "Games on Demand." and i also had, songs for rockband 2, movies, and avitar items downloaded as well, and now they are all gone. and when i try to re-download them, it makes me pay for them again. I had Battlefield: Bad Company, Assassins Creed, Trials HD, Worms, Saints Row 2, Call of Duty (1), Call of Duty 2, Call of Duty 3, Battlefield 1943, the first map pack for Call of Duty Black Ops, Gears of War (1), Tom Clancey's Ghost Recon 2, and a few other games that i cant remember. Now none of them are available for me to play, but it still shows them on my hard drive, and when i try to download them again, it doesnt let me. it says i have to buy them again. i also had all extensions for Saints Row 2. i have had the same xbox for almost four years, and i have gone to my hard drive, and it shows all of the saves i have for each game, but it says i dont have the actual game. and on some, it says the actual game is on my hard drive, but it still makes me buy them again. and the avitar itmes are on my hard drive, but i cant access them, and i have to but them again. I signed in under the gamertag that i bought everything with, and i still have to buy it. i have had the same XBOX not Account, for almost 4 years. this is the third time i have posted this, and i can never reply to the email i get. i have tried signing in, ive looked at the game to see if i can download it again and i cant. i havent deleted anything from my hard drive, and havent changed anything on my account. they all disappeared  after the latest update for the dashboard. I also went to my download history, and it says i have nothing downloaded. its completely empty. What do i do?