iPhoto won't complete calendar order, but does complete book order

I want to order a calendar I made in iPhoto 11, but everytime I get to the end of the upload this happens:

I've tried ordering it is safe mode, and with the firewall turned off - doesn't work. I've also tried reinstalling iPhoto and using a different AppleID - still the same result.

However, to test whether it was an issue with my account or with the photos I was using, I attempted to order a book that was filled with many of the same photos I used in my calendar and it went through perfectly! Why can't I get a successful order with the calendar?