Feeds can go bad when they start hanging around with the wrong group of kids.
Actually, the most common cause of feed problems is the content that you post. A lot of folks like to use Microsoft Word (or other word processors, we just know this one has caused us a lot of headaches) to write up their blog posts.
When they do, sometimes these word processors can sneak in characters that are very difficult to render in XML. The most likely culprit is the dreaded Smart Quote, especially it you are putting quotations in your feed posts. Also, Word (we think) likes to put in special tags for formatting paragraphs, as well as address information. We don’t always know where these things come from, we just know that when they are introduced, they cause problems.
So how do I keep that junk from coming into my feed/blog?
Our best advice is to compose your postings in a straight text editor, like Notepad on Windows, or TextEdit on the Mac. You can get away with putting HTML tags in your posts, as most blogging engines correctly format those tags for placement inside a feed.
See this earlier blog post with an explanation on how to add your Microsoft Word content to a post or page without taking down your site: Why Can’t I Copy and Paste Content Directly From MS Word?