So I download all the mods that I and my friend want to play with. After playing for a while we decided to add Biomes o' Plenty mod.
When I click the download icon on the version of Biomes o'Plenty, It spins around and eventually an error message pops up.
After the error msg, When I check the files all the mods are gone and I have to re-add everything, And when I add Biomes o'Plenty mod again, Same thing happened. 
This is the error picture:
