This discussion at apple.com was quite helpful:
https://discussions.apple.com/message/6172636
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The latch mentioned in the instructions that releases the stand to move to the fully forward position needs to be pushed in again to allow the stand to move back to the normal upright position.
The latch that you push in with the card while you are removing the base is simply harder to hit when the unit is in the fully forward position. The card has a tendency to slide off the latch when you push up on it and there is much more space underneath the internal latch with the stand in the forward position so it's easier to miss it. The other trick to this is that the stand has a natural tendency to want to push back on the latch making it hard to move. You need to make sure that the stand is pushing all the way forward or the latch will be wedged on the stand and won't move.
When you have hit the latch and pushed it back and up you can move the stand back to the upright position and then release the latch.
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