I found the solution, but not why.
In rss-image-feed/class-lib//A5_ExcerptClass.php line 50:
$text = preg_replace('/\b(https?|ftp|file):\/\/[-A-Z0-9+&@#\/%?=~_|$!:,.;]*[A-Z0-9+&@#\/%=~_|$]/i', '', $text);
Commenting this line works OK. What is its function?
