I upgraded to 1.9.2.2 yesterday and after that there is an issue that customer couldn't register on the website. Thought it was just user error, but then I tried it myself and it was indeed broken. There is no error but customer redirecting back to create account page. After a few minutes found that need to update the customer registration form template, which is updated in Magento 1.9.2.2 (and security patch SUPEE-6788). So you need to update following file if you have same issue.

template/customer/form/register.phtml (line 46)

OR

template/persistent/customer/form/register.phtml (line 45)

Then added following line:

<input type="hidden" name="form_key" value="<?php echo Mage::getSingleton('core/session')->getFormKey() ?>" />

I hope this will help someone.