I see that no one here has mentioned proxyban (evil fees) yet. Could it be that the user registered an account from an abused IP range and is required to pay an evil fee in order to post?
When you register, the IP that you used when you submitted the registration form is used to calculate your evilness. The more frequently this IP or its neighbors were banned, the more evil is associated with your account. The amount of evil associated with an IP decays slowly over time, but the amount of evil associated with an account does not. You must pay or be manually whitelisted to enable posting on one of these "banned" accounts.
If this is the case, there is a topic started by LoyceV on how to remove the evil fee for free:
Remove Proxyban (evil fees) - email to get whitelisted for freeit is possible but I've read somewhere that the account will receive a message saying that they can't post or send PM due to evil points. it would be nice if OP could clarify whether his friend's account received such a message after creating the account.