I received a check from a customer and the IRS took the funds. What can the customer do to me?

Hello. A nightmare at best. I received a check for $5700 from a customer to do a job. I deposited it in the bank, just like I've always done, and the IRS liquidated my account. Now I have nothing, and the customer is irate, (understandably so). I have communicated with them consistently through this, but, without affirmative answers, I just don't have the money to follow through. I told them I will have to earn it and pay them back. They have family calling me haring me, accusing me of running off, etc. I have not run off, and I tell them so. I can prove the account was liquidated. I am sending a certified letter stating such as well as a payment plan to pay them back. Is there anything else I can do? What can they do against me? Thanks in advance.