I preordered an album and now that its avalible Itunes will not download my order?

Why won't any of my devices download? My handheld just goes over the same pop up with out doing anything else.

1. Check for a preorder?

2. Preoder(s) is/are avalible.

3. Would you like to download?
Confirmation to all three just puts me back to the first one.

My home computer wants my billing information?

A. Dosn't the fact that it's preorderd mean I've already paid for it?

B. Was the money I already spent just part of how much it cost?

C. If B is true then Why wasn't I given this information either when I first ordered it or now?

D. Is it charging me twice for something I've already paid for?

Whenever I submit my billing information It dosn't do anything else! Itunes won't donwload my purchase.