i had exactly the same problem with my son , what i done was to sit in his bedroom with him every night but not look at him or talk to him, he would eventually calm down and fall asleep, do this for about a week then gradually move nearer and neare to the door, until eventually your outside the door but if he calls you he knows your still there, do this over the period of a few weeks until eventually you dont have to be outside his door at all he will just forget, it worked a treat for me, but remeber not to engage in conversation with him, hope this helps, i aslo found a small blanket helped.
At 2 years old 'crying it out' just isn't the answer. There is obviously something wrong for this to change so suddenly. Could you change the ritual a bit more and maybe stay in the room until he felt comfortable? I mean I read a book (or 2 ) to my son before he goes to bed then I sit in there for a bit while he goes to sleep. No big deal. Give it a try -there is obviously something that's making him uncomfortable.
