Looking more into this it seems that when a customer fills their billing and shipping info as well as payment info then go to submit, OPC does not seem to hand it off to X-cart and then reloads the blank OPC page.
Here is the message in the error log:
<?php die(); ?>
March 16, 2010, 6:36 pm -LOGIN:N/A -IP
x.xxx.xx.xx
mode=checkout&paymentid=4
March 16, 2010, 6:36 pm -LOGIN:N/A -IP
x.xxx.xx.xx
Array
(
[type] => E
[content] => ~~~~|err_payment_processor_msg| ||~~~~
)
IP was removed by me.
This has been resolved.