RSS Feed stopped working

Nevermind. It turns out WordPress SEO by Yoast was causing the problem. But, I’m not sure why. Has this happened to anyone else?

YES – Have “Yoast” – but no more “Comments” – ????

It happens to me. https://www.finanzaoperativa.com. However I have no WordPress SEO by Yoast. I just added a few days ago a plug in for related posts. However I suspect the true problem is my updating to WordPress 3.5. The error my feed shows is
XML Parsing Error: XML or text declaration not at start of entity
Location: https://www.finanzaoperativa.com/feed/
Line Number 3, Column 1:<?xml version=”1.0″ encoding=”UTF-8″?>
^
I installed Fix RSS Feed but no way.
I searched for blank lines but no way.
If you go to my feed and save the page in a xml format, the two blank lines at the beginning of the page are visible.

I don’t know what to do really.
Thanks for any answer.

@floriana.liuni: As per the Forum Welcome, please post your own topic. Posting in an existing topic prevents us from being able to track issues by topic. Added to which, your problem – despite any similarity in symptoms – is likely to be completely different.