I just got this in the middle of a shoot yesterday.. happened when i ejected the disk. It wouldn't come out...just stuck there.. I think its a prob with the carriage mech. All the people i spoke to say to send it back. I had someone had a look at it and nothing could be done.
Some hire places in the UK have had the same issue.. seems the whole carriage mech needs to be changed.
Seems that its quite a common issue. Im not pleased!