Ya know, i had this happen for some reason to my uber dagger.
It had 33 life leech on it, then for some reason it had 13% life leech the next time i checked it, i stopped using it and when i checked it sometime later the next week it had returned to 33 life leech.
Just wait a lil and see if that helps it cause i swear i thought my thing was ruined too for days and then one day it was fixed weird.