A friend and I can't seem to find it, but isn't there a rule about needing a weapon with the same enhancement bonus(+1 to +5) or higher to sunder a magical weapon?
Yeah, what you're talking about Azten was something in either 3.0 or 3.5. Back then there was a rule that you need the same enhancement bonus or higher to cause damage to an enemies weapon.
This was instead replaced by giving increased hardness and hp to weapons based on their enhancement bonus.