Hehehe, I know what you mean about that Icestorm
. Anyway, I think the hammer thing is a glitch. I was able to use it before and it hit GOOD.
Did you try reloading and then reequiping it.
If all fails and you're not able to use it, don't worry, you can get a decent price for it at the shops.
Good luck and tell us how you make out.