This is a type of glitch which appears at random times in the game, particularly when you are trying to kill your opponent.
What this serves to do is glitch your character so that you or your opponent suffers little to no damage from attacks. In essence, it eliminates your hitbox so you cannot be hit easily or at all.
It would usually take a full magazine from an Assault Rifle to get one kill. To make it even worse, enemies could still see where they're getting attacked from by the harmless bullets and turn around to finish you off, if they notice they're getting hit.
This glitch could not be manipulated at command and got many players frustrated.
Here is a Hitbox Glitch demonstration unintentionally caught on camera.
- A January 2009 patch fixed most errors, but up to March 2009 there are still people who fall victim to this glitch. Oddly enough, this glitch did not apply when attacked with a melee weapon.