Illegal Packets Banning question
 

The customer service supervisor informed me that I was banned because illegal packets were recieved that came from my IP while I was logged in. Now I lost a couple of accounts, but a couple seem to be good. My question is what could have caused this? Is it possible that the data sent became corrupted and the server mis-interpreted it has a hack? Would a router/firewall do this? Could NAT have made errors?