functions.php is corrupted error while sending invoice reminders

[taim]

I'm seeing this error while I'm trying to send invoice reminders.

Or some times I just receive blank page

on this url

clients/admin/invoices.php

Any one please guide me.

Thanks

[taim]

Every time a new customer add item to cart & register, he should be redirected to payment page of paypal, but instead they are seeing just a blank page.

But when they try to pay invoice from their account after registration, they can do that.

I don't understand why they are unable to pay at the first time, when they register.

Any one please check this out /http://www.hostug.com/clients/cart.php?a=add&pid=1

Just add this item to cart and try registering. You will be seeing a blank page when you press Complete Order!

But actually your account will be created in whmcs. And invoice will also be created.

Any one please tell me how to fix this issue?

 

And while I try to send those pending invoices to customers through email, I just see a blank page on admin/invoices.php. And some time that page shows error that "invoice.php is corrupted" Or "functions.php is corrupted"