I don't know why... but i can't sign-up

Can you describe better your problem ?
Of course!
I click on your referal link then i click on "signup" on the left side.
I wrote my username, my e-mail, my password and retype password.
Then i click on the box "term of service"
Then i wrote the captcha.
And finally i click on signup...
...and appears the same window with a red "X" without a message.
So, i try to change user, captcha... but all the time appears this "X"

Aha, I remember having this issue when I chose a password using special characters. I think it's poor practice they can't be used... but meh. Try sticking to uppercase, lowercase and numbers and see if you still have a problem.