"Your Purchase Could Not Be Completed"

I am using iTunes on a new HP computer. I've authorized the new computer and just tried to purchase a audio book and got the message, "Your Purchase Could Not Be Completed". I have confirmed my payment details are correct and that the computer is authorized. The software is up to date and I even tried purchasing it on my iPod instead of on the computer but got the same error message. Has anyone else seen this or had luck fixing it? I've contacted support but might not hear anyone respond for 48 hours. I also ran a diagnostic on my iTunes and it came back with no errors, it actually says that I can purchase. Thanks in advance!