Unable to update bundled iMove/iPhoto/GarageBand?

I purchased a new Air yesterday. Right out the box the App Store shows 3 updates available, one each for the bundled iMovie, iPhoto and GarageBand.

When I go to update them via the App Store I get a dialog that "You must have previously purchased the item being updated. Tap buy to purchase it now".

Of course if I try to do this it won't let me, I get another error "Purchase of this item is not currently available. The item is being modified. Please try again later".

The updates don't show in regular Software Update, and if I download the standalone updaters from Apple's support site the installer says they can't be installed and to use the App Store.

I seem to be going around in circles. Has anyone any suggestions please?