It sounds like the spring arm that holds the yolk in place has popped of of the yolk has slipped out of the sliding pinion, classic keyless works stuff, there is tutorial here somewhere, you will have to remove the dial, hands and date wheel to get to it but it is not that difficult once you get into it. What setting was the crown in when you removed it, Winding, date set or hand set, i find i have less problems when i remove the stem when it is the hand set position.