Okay, that was the problem, it occurs because you use an IP address that already use to create an account before or detected as it, you just need to pay some fee to be able to create a post. It will be based on the number of accounts that have been registered via the IP, the more accounts the more expensive it will be.
If you sign up from a public connection that has already been used and abused then you are required to pay a fee. Just find a IP/connection that is 'fresh' and you can sign up for free.... or just pay the required fee.