How do I make my five iron work?

A few years ago my 5 iron was one of my best clubs, meaning I got consistently good results when using this club.  My set of clubs got replaced and instead of 5 and 6 irons the new set had 5 and 6 hybrids.  I adjusted, but after awhile I decided I really missed my 5 iron and started dropping hints... lo and behold, next birthday I received a lovely Callaway Ladies 5 iron.  That first season I walloped the ball with that club!  Now, for some reason I can't seem to hit with it at all, and no, I'm not blaming the club!  I just can't figure out what I'm doing differently?  I'd love to have some suggestions!