(repeating this reply from a separate post by sevensoutbill in this forum)
Having the same issues when the latest AddThis plugin is activated.
We had to troubleshoot why our WordPress feeds weren’t working today, and there are three ASCII characters that are included in the <description> tag of our RSS feeds generated by WordPress when the latest version of the AddThis plugin is activated. (We probably didn’t notice the broken feeds when the plugin was first updated a couple of days back).
Important: Actually, it’s not really the RSS that’s the problem – these ASCII characters are being injected into the post source code, so it’s just that the RSS is breaking because the source code itself is bad from whatever AddThis is adding.
We’re seeing this in any page/post that has summaries/excerpts while AddThis is activated. What happens is that in the summary/excerpt, the first <p> tag gets three ASCII control characters after it, the ACK ENQ and BEL character codes. You can plainly see them when looking at the code in a text editor.
sevensoutbill: Find a page of yours (like a category page) that has excerpts or summaries. Copy the page’s source code into a text editor. See if you don’t see those ASCII characters right there in the source code after the first <p> tag like we’re seeing with AddThis activated. Once we deactivate AddThis, those ACK ENQ and BEL characters that immediately follow the <p> tag go away and the code looks clean (and hence, the feeds work again).
