"Internal Server Error" when emailing customer

Hello!

So, I followed a few tutorials on how to change what a Status Notification email says to a customer. I simply wanted to add a line to it saying something in the lines of "don't forget to follow us on facebook, bla,bla".
This led me to Catalog-> Language-> Mail-> order.php.
Here, I've added the desired line and after uploading the modified order.php, OC stopped sending emails. So I went back, and deleted the added line, and made the order.php file as before, uploaded that...and it still does not work.

When I try to inform the customer of the change in order status (Sales-> Orders / changing order status and checking "Notify Customer") OC says "Internal Server Error". Furthermore, OC stopped notifying me through my personal email address when I get a new order...so, I guess it's safe to say it can't send any emails.

Any ideas, suggestions?

Thanks in advance!

Hello , I am having exactly the same issue. We have tried to use many different combinations and cannot ge the mail notifications or mail marketing to work. We are getting Internal Server Error . We recently updated to 3.0.0 . Prior too this for many years it as fine.