Invalid File Format
AOL Reader only expects valid OPML/XML formats. Commonly used incorrect file formats are:
Invalid XML Format
A common issue with OPML export is HTML entities not being encoded properly by the RSS app. We have built a more robust OPML import tool to tackle that but since a lot of the entities are required as part of an XML, detecting and converting them could be tricky. For now, we have successfully updated '&' with proper encoding. The best way to address this is to inform those reader teams.
Incorrect File Encoding
If the reader's export needs you to copy and paste into a file editor in order to generate an OPML file, verify that you are saving with the correct encoding (Unicode).