RSS Error: This XML document is invalid, likely due to invalid characters. XML error: not well-formed (invalid token) at line 176, column 250
Solution
http://www.feedvalidator.org/check.cgi
Use feedvalidator to display where exactly the error occurs. In my case it was a format error or invalid characters in a specific blog article. With this tool you can find out which article it is and exactly which line you should edit in the blog article.
