Deposited for the bonus, but account was blocked immediately

I opened a live account with this broker and funded my account via WebMoney with an amount of $2,000, and then I received a $600 bonus. After only 12 hours, I found out that my account had been blocked and received an email claiming that my account had been closed because of Arbitrage! But I did not open any trade on my account at all. The most important note, in this case, is that the Broker blocked my whole balance and they did not allow me to withdraw my initial deposit ($2,000). They referred me to section 5.2 of the client agreement and claimed that they had the right to block my account, ALL of my balance, and even my INITIAL DEPOSIT! I really can not understand what is going on here...I even did not open any trade on my account. This clearly is a SCAM!!!