Hi yall,
Me too encountered this problem when I wanted to update the mail template. There is an security issue with some of the servers that you can not use some javascript in textarea's or even the words UPDATE and SELECT. This is for security reasons against crackers.
As you can see the word update can be found in the message body of New Ticket Notice (email template): You can update or view this ticket's progress online here: %url/view.php?e=%email&t=%ticket.
TO SOLVE ISSUE:
If you put this word between quotes like 'update' ....then it will be fine to save the template without the 500 internal server error
so now it will look like You can 'update' or view this ticket's progress online here: %url/view.php?e=%email&t=%ticket.
Cheers,
Marlon