xmlParseEntityRef: no name is often a sign for a single ampersand character which is not part of a htmlentity like & or è.
But line 1256 does not contain such a single ampersand in none of the 3 versions (the 2 from the pastebins and your current feed).
Also I'm really not sure that message should appear for the 8.8.10.6 and the 8.8.10.7 feed.
line 1256 from http://pastebin.com/GiLxuP0W (probably 8.8.10.6):
<itunes:subtitle>L'ospite dell'ottava puntata è Paolo, blogger di JustYourApple (il nuovo AppleLAB).
line 1256 from http://pastebin.com/4G2p9WED (probably 8.8.10.7):
<itunes:subtitle>L’ospite dell’ottava puntata è Paolo, blogger di JustYourApple (il nuovo AppleLAB).
line 1256 in your current feed:
<itunes:subtitle>L'ospite dell'ottava puntata è Paolo, blogger di JustYourApple (il nuovo AppleLAB).
In the current version none of the special characters are transformed into their numeric entities. That is okay. But it should also be okay to transform them into the numeric entities (see iTunes Podcasting Resources sub section "Using HTML Named Character Entities.")
In the feed produced with 8.8.10.6 only the small e with the grave is transformed. Shouldn't the column number in the error message be different compared to the column number in the message regarding the feed produced with 8.8.10.7 if the transformation of these characters should be the problem?
Or did you insert this character via an unusual way?
I have copied and pasted the line from the source code of your current feed into one of my test posts "undeuxoutrois.de/wp/2011/03/22/episode-with-a-whitespace-in-the-filename/" to see how it looks in my RSS feed. I have also tried to reproduce the error message with Chrome.
But in my RSS feed the e is not transformed and my version of Chrome has no problems with the feed.
Furthermore the feed is still valid as the XML code of http://pastebin.com/4G2p9WED (which was probably produced with 8.8.10.7)
The questions for me are now: Why is the e transformed into the numeric entity in your RSS feed?
and
Was the error message really the same for both the feeds from the pastebins? Or was only the line number the same?