Marketplace won't download

I'm trying to download my marketplace worlds and it stays on 0.00MB and the line never moves, when I try to cancel it, it takes me 3 click to try to cancel it and it will go back to the loading screen then I have to force close Minecraft, the only way I can get the Marketplace to work and download is if I reinstall Minecraft and I have to download all my worlds so I don't lose them and I'm tired of doing that so I'd like to get this fixed. thank you,