Thanks, that was the solution.
I just changed the line #340 in feed-podcast.php from
$itunes_excerpt = substr( $itunes_excerpt, 0, 224 );
to
$itunes_excerpt = mb_substr( $itunes_excerpt, 0, 224 );
and it worked.
The current version (3.3.1) has the problem only at line 501 in file sociable.php with the yahoo link.
Now it is version 2.5 time and still the tag cloud isn’t sorting well. Thats really bad.
And I don’t think one should point the finger to the ignorant php function. It just has to be corrected by using some other function.
Is there demand from other europeans to solve this? I really would try if it will be included in some later release.