I had the same problem, and I think i've solved it -
comment out line 147 in gelato.class.php (the one right below the
"$id_video = getYoutubeVideoUrl($url);" line add the following
return "\t\t\t<object width=\"425\" height \"344\"><param name=
\"movie\" value=\"
http://www.youtube.com/v/".$id_video."\"></
param><param name=\"allowFullScreen\" value=\"true\"></param><embed
src=\"
http://www.youtube.com/v/".$id_video."\" type=\"application/x-
shockwave-flash\" allowfullscreen=\"true\" width=\"425\" height=
\"344\"></embed></object>\n";
Hope this works for you as well
t.