Only thing I can think of is the spring that gets compressed when you unlock the hubs has come out of where is should sit when the hub has gone on the car.
Did it work properly before you put it back on?
Link below has a pic disregard the text its not mine. Shows how the inside of the hub should sit in 'free'
http://forum.ih8mud.com/attachment.php? ... 1176622245I dont think it would have anything to do with the tighter circlip the end of the CV was probably just a bit further in. IIRC vitara CV's has a holes tapped in the end an M8 bolt would fit in so that you could pull the cv through the hub and hold it there to help get the circlip on I'm not sure if sierra is similar.