Essentials: That kit does not exist or is improperly defined

Hi, I have a problem with making kits with Essentials for Bukkit.

This is my problem:
When I type /kit [kitname] this comes up:
ERROR: That kit does not exist or is improperly defined.

Any idea how to fix it?

Here's my config.yml: (The spaces are correct but doesn't show up here)

# Note: All items MUST be followed by a quantity!
# All kit names should be lower case, and will be treated as lower in permissions/costs.
# Syntax: - itemID[:DataValue] Amount [Enchantment:Level]..
# 'delay' refers to the cooldown between how often you can use each kit, measured in seconds.
kits:
pvp:
delay: 1
items:
- 276 1
- 282 16
- 306 1
- 307 1
- 308 1
- 309 1
archer:
delay: 1
items:
- 261 1 knockback:2
- 272 1
- 282 7
- 262 64
- 262 64
- 302 1
- 303 1
- 304 1
- 305 1