Hi
I too buy my Cathe dvds from CK Sales (I'm in the UK).
The first time I ordered from Cathe's site I did it on a Mac using Safari (at work) and I also had problems (had to wait til I got home to order). Are you using Explorer on a PC? That may be the reason you're having trouble.
Don't think it's to do with being an International customer cos when I eventually ordered from home I had no problems and my order arrived within the week.
Andrea