Hello!
Can you please tell me, when a user clicks "Confirm" and gets what white page, what's the error message shown? Also, what kind of payment gateway do you use for the credit cards, still paypal or just collecting cc data for offline processing, or some other payment gateway/processor ?
As about the IPN handle, you can view in my recent projects list a couple of exactly same type of projects completed. Paypal changed some things around, indeed, and this rendered many of the scripts unusable, but this is something that can be addressed, and fixed. of course.
I'm available to start working right away, I'll need ftp access and possibly phpmyadmin.
Regards,
Dragos