Guards have been edited/nerfed, depending on how you'd like to look at it.
Instead of there just being the "Guard" chip, it has been split up into three individual chips.
Guard1 is your standard Guard. It raises a shield to block a single attack, but only reflects a maximum of 60 damage. If an attack with a power level over over 60 strikes the Guard, it protects your Navi from the entire attack, but only bounces back 60 points of that damage it nulled.
Guard2 is a stronger version of the chip. It raises a shield to block a single attack, but only reflects a maximum of 120 damage. The physics of this chip are the same as Guard1.
Guard3 is the strongest Guard you can get. It raises a shield to block a single attack, but only reflects a maximum of 200 damage. The physics of the chip are the same as Guard1 and Guard2.
All the Guards you currently have are Guard1s. Edit your chip lists appropriately.
That is all.