Hotfix (2009-05-13): "The Doomguard's ability Cripple now reduces ranged and melee attack speed by 20% instead of 45%. Cripple's slowing effect does not stack with other slowing effects such as Thunderclap and Infected Wounds."
Patch 1.6.0 (2005-07-12): Targets that are immune to movement slowing effects will no longer be affected by Cripple's movement slowing effect. Melee and ranged attack speed slowing effects will still affect these targets.