Minecraft server crashes when launched.

I wanted to make my vanilla server into a bukkit server.
I launched the bukkit server, and copied vanilla-server files in the bukkit-server, but it won't launch !
Notice that i didn't delete files from the vanilla server document ! I tried to launch it, and it crashed directly, about the fifth line.

I tried by removing all files and launch it just like when i download it, but it didn't launch, without saying anything.

Don't alarm yourselves, it could also be caused by Java !