Sign

I installed a server (bukkit). When I went to write the rules for the server(without plugins), I tried to use signs. I could write on them, but as soon as I click done, the text disapeared. It happens to everyone on my server.

I tried to remove everything apart from the map, the bug was still there.
I tried to change from bukkit to spigot, still there.
I tried to reinstall my server, still there.

So then I thought that maybe my save file was corrupted. I went in SP to find out that it didn't work there, compare to everyone else. I uninstalled my game, wiped the map, and tried again. Still not working.

I wiped the map again, and, without joining, I asked someone else to go and try to place a sign... The bug was there again.

I've looked everywhere on the internet, and only found 1 post about it on Minecraft Forum. Nobody found the way to fix it...

I don,t know how I got this thing, but I really need help.