Magento Blank Page After Checkout with PayPal
If your Magento online shop is just showing a white blank page after you get through checkout - and you are using PayPal as the payment method - try these things to fix it:
1. Go to System > Configuration > Advanced and make sure that Mage_Paypal is "Enable".
If it still doesn't work after that, try:
2. Set Transaction Type to Individual Items in the PayPal configuration.
Worked for us, does it work for you?