If it’s the same error I had, that’s because of a problem of the plugin.
clearstatcache only accepts two parameters from PHP>5.3.0 on.
So UploadHandler.php should read:
protected function get_file_size($file_path, $clear_stat_cache = false) {
if ($clear_stat_cache) {
if (version_compare(PHP_VERSION, '5.3.0') >= 0)
clearstatcache(true, $file_path);
else
clearstatcache();
}
return $this->fix_integer_overflow(filesize($file_path));
}