I'm using the repeater plugin on an IIS system. Using the WP_PLUGIN_DIR constant (as well as the WP_CONTENT_DIR) causes an issue since you are using dirname(__FILE__), which has all the slashes the same, but wordpress's constants don't (I don't know why).
The fix would be to use
$dir = str_replace(str_replace('/', '\\', WP_PLUGIN_DIR) . '\\', WP_PLUGIN_URL . '/', $dir);
$dir = str_replace(str_replace('/', '\\', WP_CONTENT_DIR) . '\\', WP_CONTENT_URL . '/', $dir);
Unfortunately, adding those trailing slashes is necessary, otherwise the one before the directory name just escapes the directory name.
The fix would be to use
$dir = str_replace(str_replace('/', '\\', WP_PLUGIN_DIR) . '\\', WP_PLUGIN_URL . '/', $dir);
$dir = str_replace(str_replace('/', '\\', WP_CONTENT_DIR) . '\\', WP_CONTENT_URL . '/', $dir);
Unfortunately, adding those trailing slashes is necessary, otherwise the one before the directory name just escapes the directory name.