Why wasn't the Labour manifesto printed in time?

I tried to purchase a copy of the Labour manifesto from my local W H Smith this morning but I was told that the manifesto wouldn't be in store until the 19th. Apparently Labour's manifesto has been delayed because of "printing problems". We've got used to Labour not being able to deliver their pledges on time - now they can't even publish them on time. Perhaps Gordon Brown insisted on some last minute amendments. He, after all, hopes to be Prime Minister as soon as he can get rid of Mr Blair and will be the one who has to find excuses for non-delivery.