Problem with the locking. Not sure about your model, Some have a release button, Mine is behind the kick panel at the bottom, LH side. Otherwise you might need to take top off to release manually. Disconnect power if you do. Try giving it all a very un technical twist and shake 1st, two opposite corners on top just twist it a bit each way, not hard, might be enough to free it, if not, you will have to open it up.
SD, August 2012