shouldn't I have received some type of noitification (registered letter..) before this could have happened?
No. If they notified people they were going to sieze their accounts people would move their money -- who wouldn't ??
You apparently have a judgment against you. You have to call the courthouse in your area first thing to find out if there really is one and then get a copy of the case file. Then you can get the details about what's going on.
"Knowledge is Power - use it as you see fit !
I am not a lawyer or a member of the legal profession. My advice is based on research and experience, my own and others, some who practice law. You decide for yourself what actions you do or do not take from my advice.