In the Joomla 3.1.5 I found this error in error.log:
PHP Warning: getimagesize(/cache/thumbs/336b46a77cbb460da5111856335179c8.JPG): failed to open stream: No such file or directory in /plugins/content/smartresizer/smartresizer.php on line 468, referer:
beta.wroclawskakomunikacja.pl/