I don't see any other way to handle the issue except for diplomatic. Let's face the fact: if Iran would build the missile, Poland shield couldn't help. Well... there's one more way - to invade Iran right-away but this hardly possible. I don't think the world society will allow to the US another Iraq.
Sasha, interestingly enough it seems you and I see things pretty similarly here (sorry I've been away for a few hours, guess there's a war going on here or something..)
My suspicion is that Iran already has the missiles, and is now just trying to get something "special" for a payload. After all, as you and I both know, the technology for launching a warhead and for launching a satellite...are the same, and Iran has just done exactly that, contrary to many who thought they weren't so far along.
I do think the shield would help against Iran. It may not stop a cold-war style onslaught, such as the U.S. or Soviet Union were threatening each other with, but I think it could be effective against Iran.
Finally, while I agree there is perhaps reason to invade Iran right away, there are far too many naysayers who feel that the U.S. invents everything from thin air and is just picking on people....so I would say, why not Russia? I know Russia has oil deals with Ahmadinejad, but hey, if the Russian army were to roll through Iran...the ICBM threat would be countered at least. The new government of Iran will still need to sell its oil, at any rate, and new deals could then be brokered....its a thought, and it would take away from all those who distrust everything the US does. Of course, then there are probably just as many who distrust what Russia does, as well.