Inventory.addItem() not working

[MikiAsano]

Hi! I develop a plugin, and using player inventory,
ItemStack is = new ItemStack(Material.BED,1);
inventory.addItem(is);

I have tried all ways to use Inventory, but completion is not working.
plugin "non-complying" all code after this string inventory.addItem(is);
I using bukkit 1.5.2 api, but on the other does not work.
Help me =)

[MikiAsano]

And not wroking command /give (CommandBook) and //wand (WorldEdit) too.

In what's described the interaction with the player's inventory (not an abstract class)? I would like to correct the problem