Can't break any block with adequate tool in Adventure mode

I was making a map on a server and when i switched to adventure mode for tests i took a diamond pickaxe and wasn't able to break an obsidian block. Then i tried to break grass block with a gold shovel and it was impossible too.

Then i tried on a solo map and the same happened.

I join a video for evidence http://youtu.be/zaWqhxSkCXQ