They can freeze your account for many reasons. A friend of mine had his bank account frozen for suspicious activity. He was depositing many small denomination US currency into different ATM machines throughout the city between the hours of 3:00 and 5:00 AM every day. I know, pretty suspicious huh. What was he up to? He was a taxi driver. The account freeze caused checks to bounce along with insufficient fund fees. Each night he would lease the cab to go to work. But since his money was frozen by the Department Of Homeland Security he was unable to work. He got it all sorted out with the bank after a couple weeks.