Try changing line 257 of 'application/views/event/calendar.php' from:
<?php echo (strlen($subject) < 15 ? $subject : substr($subject, 0, 14).'...')?>
to:
<?php echo (strlen_utf($subject) < 15 ? $subject : substr_utf($subject, 0, 14).'...')?>
You need to have the PHP extension 'mbstring' to handle non-english languages correctly.
The problem is that when using the substr function on a multi byte character string, if a wrong string length is given, it may cut the string in the middle of a character and, for some reason that I ignore, this causes PHP (or Apache or something else) to stop sending the rest of the page. Instead of gracefully recovering of the problem by changing the invalid character for something else, it just dies.
