If you use the Language Override and the existing text has a quotation mark which is escaped, the escape character is not added to the override.

SO:

$_['text_register_account'] = By creating an account you will be able to shop faster, be up to date on an order\'s status, and keep track of the orders you have previously made.';

BECOMES:

$_['text_register_account'] = 'Make an account if you expect to use us again, otherwise use Guest Checkout. By creating an account you will be able to shop faster, be up to date on an order's status, and keep track of the orders you have previously made.';

In the word ORDER the escape \ is missed.

And that kills the page