I'm going to have to agree with Andy. I don't think you're going to have much of a leg to stand on, Bruno. If the current owner of that account were pretending to represent your company, or was even just using it to bad-mouth your brand, then you might have some luck and I'd say more power to you (though I still wouldn't have any idea what channels you need to go through). But that's just some dude, and Twitter is never going to give you his username because you want it.

I say this as someone in that dude's position. I happen to share the same name as some popular Christian rock musician, and I get tweets for him all the time. That guy had to choose a different username when he joined because he got there after me. If I had been impersonating him, Twitter probably would have helped him out (I've heard of it happening).

If I were you, I'd immediately go grab "twistedmeloninc" so I at least would have a decent username. It doesn't really matter too much if your name isn't exact, because I think if someone actually wants to follow you they'll search for you or they'll get to your account through your website or places like your email signature (if you choose to do that).