Divorcing an Illegal Alien

Can an illegal alien file for divorce from a U.S. Citizen? we got married in a different country and he assured me that he wanted to come to the U.S. for me and not for any other opportunities. After a couple of months with him being in the states, he started picking fights fo no reason and he took off. Naturally, I was angry so I went to the office of immigration to talk to the peple there and they told me to write a letter stating what had happened and they put it in his file and counted the case as a fraudulent marriage. They told me that once his greencard expired he would be illegal. His greencard expired in November of 2007. A couple of days ago I received a form for a request to enter default from the superior court. the problem is that I never got the first forms to sign and I had no idea he was filing for divorce. I would have filed for divorce myself when he first left but I didn't have the money to file. My fear now is that he could have gotte fake papers from somewhere and/or gone to the 2 year immigration interview with someone he paid to be "me" that also had fake paperwork. He could have also forged my signature on the divorce papers. Where do I go from here?